Illicit drugs

Psychoactive drugs are known to alter the mood, thoughts, and consciousness of an individual. Throughout the years, scientists have conducted numerous research and studies to increase our understanding of psychoactive drugs. 

As a result, we can make a summary of how psychoactive drugs work and explain the reasons why millions of people have turned to use these drugs to the extent of becoming dependent and addicted, despite the potential danger the drugs pose.

This article takes a deeper look at psychoactive drugs, their use, and their dependence. 

What is substance dependence? 

It can be described as the lack of will/strength/desire to quit using a particular drug. This chronic condition can also result from biological and genetic dispositions. Substance dependence can be hard to overcome; however, different forms of treatment do exist, including pharmaceutical and behavioral options.

Unfortunately, there is still a widespread stigma associated with drug dependence at this time and age, which ultimately deters an individual from seeking the proper treatment they ought to be accorded. The stigma could also be a stumbling block to policy implementation regarding drug use, prevention, and treatment. 

Having a deeper understanding of psychoactive drug use and dependence helps to sort out minor and major misunderstandings, eliminate negative stereotypes and unwarranted stigma. This article also covers;

  • Global statistics on the burden imposed by drug use and dependence
  • Consequences of mild and chronic substance dependence on an individual and society at large
  • A more in-depth look into the common effects of substance dependence across the globe
  • How the use of psychoactive drugs affects the brain
  • Environmental and genetic factors that might contribute to or protect an individual from substance use and dependence
  • Various treatment options for drug dependence

Global use of psychoactive substances and burden to health

Globally, the use of tobacco, alcohol, and several other psychoactive drugs is growing exponentially, which has increased the global burden of health.


CountryAnnual per capita consumption of cigarettesPrevalence of smoking (%)
Sri Lanka37425.71.713.75.8

The table above highlights the prevalence of tobacco use in various countries. The sample population consisted of youths and adults, both men and women. The survey results indicate that the smoking trend is growing more popular in developing countries, where currently, 9% of the female population and 50% of men smoke.In developed countries, 22% of women and 35% of men consume tobacco-infused drugs. China is the leading developing country in tobacco consumption.


Similarities between alcohol and tobacco

  1. They are both legal for consumption.
  2. They can be found in most parts of the globe.
  3. Both are the subject of numerous aggressive advertisements and marketing campaigns involving young people. 

The image above shows the alcohol status report globally. In developed countries, the rate of alcohol consumption has dramatically dwindled. However, in the same twenty years, its consumption has significantly increased in developed and former soviet nations.

Illicit drugs  

Statistics obtained by the UNODC show that there have been increasing cases of illicit drug seizures worldwide in the recent past. Access to drugs like cocaine, heroin, and crystal meth is highly dependent on cultivation levels in countries where they are sourced from and how stringent the measures that have been put in place to curb drug solicitation are in relation to the failures and successes of drug traffickers. 

Unfortunately, despite the authorities being vigilant on drug use, it is hard to hear of an illicit drug shortage in any country. Users always have enough to meet their needs. 

According to UNODC statistics displayed in the image above, it is estimated that around 200 million people across the globe use at least one form of an illicit drug. Cannabis is the most used drug globally, with over 162 million users, followed by amphetamines, cocaine, and finally opioids. 

Illicit drug use is primarily practiced by males, similar to alcohol and tobacco use. Young people predominantly use these drugs as opposed to older individuals. 

The data shows cannabis users account for 2.7% of the total global population, with 3.9% of children as young as 15 years and older had tried once or more between the years 2000 and 2001. 

2% of youths in developed countries admitted to using heroin, and 5% reported cocaine use at some point in their lives. This was in Canada, the United States, and some European countries. In western Europe and in the USA, 8% and 20% of youth have admitted using at least a single form of illicit drug aside from cannabis, respectively. Teenagers in Asia and Europe have begun a new trend of seeking the thrill of amphetamine for stimulation. 

Using syringes to administer drugs pose a significant risk of contracting numerous types of diseases, including HIV/AIDS.

What impact does psychoactive have on a user’s health?

This section comprehensively looks at the global health burden resulting from psychoactive drug use and the short- and long-term effects of using these drugs.

Global health burden caused by psychoactive drugs

The data displayed above represents the World Health Organization’s global burden of disease and injury statistics. Using DALYs, which is the standard measurement for the global burden of disease, WHO was able to come up with estimates of the amount of burden placed on society as a result of premature death and years that an individual has or had lived with disability due to alcohol, tobacco, and illicit drugs consumption. 

According to the assessment, tobacco and alcohol were the lead causes of death and disability in developing countries. The effects of tobacco use are expected to rise in other parts of the world. 

The statistics offer sufficient proof that the burden of health caused by psychoactive drug use cumulatively is quite extensive and alarming at 8.9% using DALYs. When GBD’s findings are scrutinized, we can clearly see that the main threat to the global health burden is the legal rather than the illegal drugs. 

Tobacco and alcohol ranked 4th and 5th respectively in the list of leading risk factors for preventable disease burden. Having contributed to between 4.0% to 4.1% of the global burden of bad health in the year 2000, tobacco and alcohol remain a significant threat due to the prevalent use of the substances. Illicit drugs only contributed to 0.8% of the ill-health burden. 

Short and long-term effects of psychoactive drugs consumption 

The main reasons why people take psychoactive substances is to seek their medicinal benefits or for recreational/social reasons. However, these types of drugs carry a risk of harm which can be either short or long term. 

The adverse side effects of psychoactive drugs can be classified into four categories, as shown in the figure above. First, a user can suffer from a chronic health-related condition like liver cirrhosis resulting from excessive alcohol consumption and lung cancer from continuous use of tobacco.

Also, heroin users may contract diseases like HIV and hepatitis B and C from sharing injectables with other users. 

The second category involves accidents or injuries. Examples of such incidents include; alcohol and opioids overdose that results in death or permanent brain damage. Also included in this category are injuries/deaths caused by a psychoactive drug’s interference with the user’s coordination, sound judgment, or concentration. 

Driving under the influence of a psychoactive drug and causing a fatal accident also falls under the second category and assaults and suicides. 

Acute and chronic social problems are featured in the third and fourth categories. The former category comprises an arrest or an unexpected pause/break of a close relationship, likely a romantic one. Chronic social problems could include disinterest and consequently the neglect of professional and family responsibilities.  

How can we best define drug addiction?

  1. A strong desire or sense of compulsion to take the substance;
  2. Difficulties in controlling substance-taking behavior in terms of its onset, termination, or levels of use;
  3. A physiological withdrawal state when substance use has ceased or been reduced, as evidenced by the characteristic withdrawal syndrome for the substance; or use of the same (or a closely related) substance to relieve or avoid withdrawal symptoms;
  4. Evidence of tolerance, such that increased doses of the psychoactive substance are required to achieve effects originally produced by lower doses;
  5. Progressive neglect of alternative pleasures or interests because of psychoactive substance use increased the amount of time necessary to obtain or take the substance or recover from its effects.
  6. Persisting with substance use despite clear evidence of overtly harmful consequences, such as harming the liver through excessive drinking, depressive mood states consequent to heavy substance use, or substance-related impairment of cognitive functioning. Efforts should be made to determine that the user was actually, or could be expected to be, aware of the nature and extent of the harm.

The list above highlights the ICD-10’s six criteria that one can use to determine if their use of psychoactive drugs has reached the addiction stage. Ticking to three or more of these six signs within the last year makes you dependent/addicted to psychoactive drugs.

Only the third and fourth criteria can be easily measured using biological means. Number three covers withdrawal, i.e., experiencing uncomfortable and unpleasant psychological, mental, and physical signs and symptoms after discontinuing or reducing the use of psychoactive drugs. The fourth criteria talk about tolerance – whereby a user’s body builds a resistance to the drug’s effects in small doses, thus the need to up the dosage to achieve similar results you were getting with smaller quantities in the past.

The other criteria, four in total, are difficult to quantify through biological measurement since they involve a cognition aspect. However, it is possible to make a measurement using modern and up-to-date neuroimaging techniques. 

Substance dependence as a brain disorder

Substance dependence disorder results from the effects of continual use of psychoactive drugs, which distorts the brain’s normal functioning. The drugs interfere with the user’s brain’s normal and standard emotional, perceptual, and emotional processes.

How can one tell if the brain or any other body organ is not functioning accordingly? Well, the first step is to understand the qualities of a functional body organ; from there, it is straightforward to tell when it’s not performing at optimum levels.

As for the brain, we can decipher its functional capability through a person’s behavior or thought process. A brain’s abnormal functioning can trigger complex and drastic behavioral indicators. When the brain suffers from epilepsy, Alzheimer’s disease, stroke, Parkinson’s disease, and many other types of brain diseases and traumas, the effects are illuminated through behavioral changes, which are considered part of the brain disorder. 

The same case applies to psychoactive drug dependence. The complex behavioral effects result from the impact the drugs have on the user’s brain (short and long term).

In the past, mental and psychiatric illnesses were not considered brain disorders, but researchers discovered that these conditions alter the brain’s normal functioning with time. As for psychoactive drug dependence, there is a ton of research and resources poured into the making of new technologies that can measure and depict a clear picture of just how short- and long-term use of drugs can distort the brain at a molecular and cellular level.

Neuroimaging techniques that result from years of neuroscience research have made it easy for medical researchers to visualize the brain structure and its functioning process. Using neuroimaging techniques, it is now possible to track what happens in the brain by viewing the functioning of the various receptors, noting metabolic process changes, and exploring the brain’s multiple regions via the flow of blood in those areas. 

Scientists can also observe the effects of substances when they are introduced into the brain. They could also check the impact of continual use of these substances on the brain’s normal functioning.

Such techniques include MRI or magnetic resonance imaging, which utilizes radio waves and magnetic fields to make top-notch quality images of the brain and its various structures. The images could either be two or three-dimensional and are usually static. For functional brain imaging, functional magnetic resonance imaging is performed. It provides information on brain activity by comparing oxygenated and deoxygenated blood available in the brain. 

 Another imaging technique includes PET or positron emission tomography, which displays a person’s metabolic activity by focusing on a particular brain region. This is achieved by injecting an individual with a safe radioactive substance and tracking its movement into the bloodstream until it reaches the brain. The PET offers viewers two- and three-dimensional images. Depending on the radioactivity levels, the PET scan will display different colors; blue and green indicate low activity, whereas red and yellow indicate high activity.

Using PET scans with various compounds can help display blood flow, drug availability and concentration in the brain, and glucose or oxygen metabolism. The possibilities are endless.

Neurobiology and Neuroanatomy

The brain is diverse and complex. It is divided into different sections that perform specific tasks. All these parts work in harmony to facilitate optimum body functioning. For example, the hindbrain provides a haven for structures that control vital body functions like breathing and staying awake. 

The midbrain supports learning of internal and external stimuli as well as motivation. It also promotes behaviors that contribute to sustenance and pleasure, like drinking and eating. It is vital when it comes to substance use and dependence. 

The forebrain is highly complex; the cerebral cortex is part of the forebrain, and it is responsible for general planning and abstract thoughts. It also does the associations of memory and ideas. Through brain imaging, scientists have discovered that particular brain areas are stimulated by the same type of stimuli that induces an individual’s craving in the period where they experience substance dependence. Some other forebrain regions have been discovered to perform below optimum level following mild or severe substance use and addiction. 

Communication in the brain happens between cells or neurons. The latter achieves the communication process by using chemical messengers, which are released at synapses (check image above).

 When a neuron experiences stimulation, an electrical signal is sent from the cell body and goes through the axon process to send the message to nearby neurons or to pass it to other regions of the brain. Chemical messengers are transmitted from the presynaptic neuron to the postsynaptic neuron, i.e., from the neuron sending the message to the recipient neuron. Some well-known and studied neurons applicable during substance use include serotonin, norepinephrine, dopamine, glutamate, and GABA. 

Chemical messengers in the brain are numerous in number. Neurotransmitters are known to bind to specific receptors, which results in the alteration in the postsynaptic membrane perfectly. Receptors are named after the transmitter they blend and bind to, for example, serotonin receptors and dopamine receptors. 

How do psychoactive drugs relate to neurotransmitters? The drugs can mimic the effects of our body’s neurotransmitters. They inhibit normal brain functioning by interfering with its normal functions. They also interfere with the regular storage, release, and removal of local neurotransmitters.  

Psychoactive drugs inhibit the reuptake of neurotransmitters following their release from the presynaptic terminal, which results in an exaggeration of the neurotransmitter’s effect. Agonists are psychoactive drugs that support the normal functioning of the receptors, and antagonists do the opposite by inhibiting receptors’ normal functioning.

How does each psychoactive substance act in the brain?

Psychoactive drugs can be divided into the following categories;

  1. Depressants like alcohol, sedatives, and volatile solvents
  2. Stimulants like cocaine, nicotine, and ecstasy
  3. Opioids like heroin and morphine
  4. Hallucinogens like PCP, psilocybin, and LSD
SubstanceHow it worksToleranceWithdrawalEffects of prolonged use
Ethanol (alcohol)Alters the effects of the neurotransmitters glutamate and GABA. Probably increases activity in the dopamine system involved in motivation and learning.Develops due to increased processing in the liver and changes to receptors in the brain.Withdrawal from long-term use can include shaking, sweating, weakness, agitation, headache, nausea, vomiting, seizures, and delirium tremens.Changed brain function and structure, reduced mental capacity, decreased brain volume.
Hypnotics and sedativesEnhances the effects of some neurotransmitters (e.g. GABA).Develops quickly due to changes in brain receptors.Anxiety, alertness, restlessness, insomnia, excitability, seizures.Memory problems.
Inhalants (volatile solvents)Like other sedatives and hypnotics, probably affect specific transmitters. Increases activity in the dopamine system involved in motivation and learning.Some tolerance develops, but is difficult to estimate.Increased susceptibility to seizures during withdrawalChanges in how dopamine works in the body, problems in the nervous system, reduced mental capacity; psychiatric problems
SubstanceHow it worksTolerancWithdrawalEffects of prolonged use
NicotineActivates specific receptors. Increases the production and release of dopamine.Develops through metabolic factors, as well as receptor changes.Irritability, hostility, anxiety, unease, discomfort, depressed mood, decreased heart rate, increased appetite.It is difficult to separate the health effects due to nicotine from the effects due to other components of tobacco.
CocaineProlongs the effects of transmitters such as dopamine.Perhaps short-term tolerance.There is not much evidence of withdrawal.Depression is common among dependent people who stop using the drugAbnormalities in specific regions of the brain, loss of some mental capacity, problems with movement, decreased reaction times.
AmphetaminesIncrease the release and prolong the effects of dopamine and related transmitters.Develops quicklyFatigue, depression, anxiety and intense craving for the drug.Sleep disturbances, anxiety, decreased appetite; changes in dopamine brain receptors, changes in metabolism in some parts of the body, reduction of mental capacity and deterioration of movement.
EcstasyIncreases the release and prolongs the effects of the neurotransmitter serotonin.May develop in some individuals.Depression and insomniaDamages some brain systems, leads to physical changes and to changes in behaviour.Long-term psychiatric and physical problems such as loss of memory, problems with decision-making and self-control, paranoia, depression and panic attacks.
SubstanceHow it worksToleranceWithdrawalEffects of prolonged use
OpioidsActivate specific receptors that are abundant in an area of the brain that is involved in motivation and learning.Due to short-term and long-term receptor changes, and to changes in the way some cells communicate.Can be severe.Watering eyes, runny nose, yawning, sweating, restlessness, chills, cramps, muscle aches.Long-term changes in certain receptors.Changes in learning and in the response to stress.
SubstanceHow it worksToleranceWithdrawalEffects of prolonged use
CannabisActivates specific receptors. Affects the dopamine system involved in motivation and learning.Develops quickly.Withdrawal is rare perhaps because cannabis remains in the body for a long time.Long-term exposure may produce long-lasting reduction of mental capacity. May make mental illness worse.
Hallucinogens (such as LSD and PCP)Different substances in this class act on different brain receptors.Develops quickly.There is no evidence of withdrawal.Short or long term disturbed mental state in which a person experiences hallucinations, delusions, personality changes and loss of contact with reality. Flashbacks or re-experiencing of drug effects, long after drug use.
(Scroll Left and Right to read the table)

As shown above, different psychoactive drugs offer varying effects. This is because each interacts differently with the brain’s elements, particularly the brain receptors, to either inhibit or promote functioning. 

Also, the drugs possess diverse effects that alter a user’s behavior either mildly or drastically. Depending on several psychological and physical factors, users will experience different tolerance build-up, varying effects (short and long-term), and differing withdrawal symptoms. 

Contributing to the theories of substance dependence development are the similarities in how these drugs affect the vital segments of the brain responsible for motivation.

The development of drug addiction. How does it happen?

What causes drug dependence in drug users?

Dependence as a learning process encompassing specific brain regions 

Dependence development can be viewed as one of the many ways to trigger a learning process. How? Enduring changes in behavior result from interactions with psychoactive substances and their associated environments. 

When a person takes a psychoactive compound, it activates certain brain regions that cause pleasurable feelings. The result is rewarding and reinforcing, making it highly probable that the user will seek that thrill again and again.

Unfortunately, the rewarding and reinforcing effects associated with substance use cannot account for the ability of some psychoactive compounds-associated behavior being applicable in all the six criteria used to determine drug dependence. 

Withdrawal symptoms might explain why users go back to using psychoactive drugs after attempting to quit but cannot explain why individuals go back to drug use even after years of remaining sober and drug-free. 

What do psychoactive drugs have that would make a user neglect his/her career and family while drowning in substance use? What causes substance-seeking behavior that leads to the user ignoring vital life activities? What causes addiction and relapse? The answer to these questions lies in complex neurobiological, psychological, and psychological factors. 

Biobehavioral tendencies that trigger dependence 

Over time, the human brain has developed vital systems that guide and direct them toward critical survival incentives. For example, the stimuli that focus on water, food, or a mate trigger a specific brain pathway that supports the behaviors that enable them to acquire the necessary goals.

A psychoactive, though subtly, does activate the same pathways that trigger an increase in motivation to continue with the substance use. 

Mesolimbic dopamine pathway

When looking at the effects of the psychoactive compounds on the brain, we found out that each has its action mechanism. What was not included was the substances’ ability to activate the mesolimbic dopamine pathway. The actions vary from substance to substance. 

The dopamine pathway can be found in the midbrain section of the brain, and it is quite involved when it comes to psychoactive substance dependence.

The ventral tegmental area (VTA) and the nucleus accumbens found in the midbrain play a vital role. These two areas communicate back and forth. The former contains numerous neurons filled with dopamine, responsible for thoughts, emotions, planning, and implementing behaviors. The latter assesses the motivational value of stimuli and promotes learning and motivation. Psychoactive drugs facilitate the increment of dopamine release in the nucleus accumbens, which positively contributes to reinforcement. 

Motivation and incentive

These two factors play a massive role in regards to substance dependence. As seen above, the mesolimbic dopamine pathway is closely associated with the boost of the motivational process. This means that survival-related stimuli take priority in the brain.

Motivation is the generous allocation of attention and behavior-related resources to stimuli according to their perceived effects/benefits. An example is when a person is thirsty, the visual and olfactory stimuli related to water (incentive) will have a considerable impact on the individual. They will take steps towards acquiring the water for consumption. If the person is exceptionally hydrated and on the verge of collapsing, he/she might steal or go against the set laws to acquire the water. This is referred to as incentive-motivational responding. However, if the individual is not thirsty, the incentive (water) will have little to zero impact on stimuli. 

The same happens when it comes to substance dependence. The drugs continuously activate numerous motivational systems located in the brain that are generally triggered by significant stimuli such as water, danger, food, and mates. The drugs trick the brain into believing that the psychoactive drugs and their linking stimuli are biologically vital. Continued use of these substances increases the behavioral and neurochemical response of the brain towards the substances.

Incentive sensitization refers to the increased behavioral and motivational value of psychoactive drugs and the stimuli/incentive linked with their consumption. 

Earlier on, we posed a question on why a person who has abstained from drug use for many years could relapse easily. Well, through the associative learning process, stimuli such as objects, surroundings, and people can activate the motivation of substance use. This causes a burning desire that often overwhelms an individual, leading to relapse, even after total abstinence from drugs.

This rules out withdrawal symptoms as the main reason individuals fall back into substance use even after quitting for years. Situations can largely contribute to such an occurrence. 

The role of genetic factors in drug use and addiction 

Around the world, you will find millions of people who have experimented with various harmful and potentially-addictive substances, and yet a majority never fell into dependency. This tells us that we are all different and drug addiction susceptibility differs from person to person. This difference can be accounted for by genetic and environmental factors. 

Biological, environmental, social, individual, and cultural factors all work together to increase or lower the chances of an individual engaging in drug use and if they will fall into dependence or not. The table below looks at these risk and protective factors.

Risk factorsProtective factors
Environmentalavailability of drugspovertysocial changepeer cultureoccupationcultural norms, attitudespolicies on drugs, tobaccoand alcoholEnvironmentaleconomic situationsituational controlsocial supportsocial integrationpositive life events
Individualgenetic dispositionvictim of child abusepersonality disordersfamily disruption and dependence problemspoor performance at schoolsocial deprivationdepression and suicidal behaviorIndividualgood coping skillsself-efficacyrisk perceptionoptimismhealth-related behaviorability to resist social pressuregeneral health behavior

Neuroscience research also looks into the actions of psychoactive drugs in relation to genetic similarities in humans. The contrast research to this looks into how the drugs act on different individuals due to their genetic disposition. 

Aside from environmental, cultural, and social factors, an individual’s genetic composition does add weight to determining how that person will react to a drug and whether their drug use will lead to dependency or not. The problem is that it is tough to pinpoint the exact genes responsible for drug use and addiction.

While conditions such as Huntington’s disease involve the abnormality of one gene, it is not always the case with other conditions. You will find some complex diseases that combine several genes abnormality coupled with various environmental factors. Psychoactive drug dependence falls under the complex category. As a result, an individual who possesses genetic susceptibility to substance dependence is more vulnerable to psychoactive drug exposure than someone who isn’t.

This phenomenon makes the study of the relationship between specific genes and substance dependence very hard to accomplish. That notwithstanding, great strides have been made in this field, particularly on identifying the particular genes responsible for substance dependence. Through studies to determine inheritance patterns in families, scientists have established the genetic contribution towards substance dependence. In families, they look at identical twins, fraternal twins, and adopted persons.

Alternative studies look into the inheritance of similar traits to figure out the regions of genes that are vital. The candidate gene studies look at genes suspected to be responsible for substance dependence; for example, the opioid receptor genes might cause opioid addiction. 

According to research, there is a likelihood that a variety of genes are responsible for the instigation of smoking and its continuation into a smoking habit. The genes responsible for the metabolism of nicotine pose a serious risk for smoking. A disparity in these genes likely determines the nicotine levels and their accumulation in the brain.

Alcohol dependence and frequency of use could have significant heritability. The possible culprit genes might be those associated with the metabolism of alcohol. The receptors for various neurotransmitters like dopamine, serotonin, dopamine, and GABA could also be vital in the association of alcohol dependence. In addition, the difference in genetics for the metabolizing enzymes could also cause fluctuations in alcohol consumption.

Genetics plays a role in the consumption and addiction of the combination of tobacco, alcohol, and psychoactive substances. While making an estimate, we can conclude that relatives of individuals affected by substance dependence have an 8X increased risk of falling into the same predicament than those whose relatives are not drug-dependent. This applies to substances like cocaine, sedatives, and opioids.

These findings are an indication that research on substance dependence is heading the right way. There is so much promise that genetic studies provide. With such information, individuals can better understand the origin of drug and substance use and dependence and how risk factors differ from one individual to the next.

As soon as the culprit genes are identified (those that predispose people to drug use and dependence), the next challenge will be determining how the specific genes interact with various environmental factors to instigate dependence. With such information, forming a reliable diagnostic and coming up with effective treatments will be straightforward.

It will be easier to identify individuals who are more susceptible to drug use and dependence in relation to one or more psychoactive drugs through genetic screening. Unfortunately, the identifications made will be based on probabilities as opposed to certainty, which raises numerous ethical issues.

In a case where the screening comes up positive for a particular drug disposition, actions like notifying the affected person or their parent if it’s a child will be expected. Further, the person or child will have to go through preventative interventions to lower their susceptibility to drug use and dependence. The ethical issues that might arise might center towards privacy, acquiring consent for treatment, and confidentiality.

Genetics may affect/influence the following aspect of drug use;

  1. Toxicity levels of a substance
  2. Withdrawal impact 
  3. Levels of psychoactive drug craving
  4. Subjective pleasurable effects 
  5. The potency of psychoactive effects of a specific formulation and dose of a particular drug
  6. Tolerance development

How can drug addiction and mental illnesses coexist?

It is not new nor uncommon to see a co-occurrence of psychoactive drug dependence in people who have existing mental illnesses. The implication of this coexistence is either there is a shared neurobiological source for both conditions, or there is a crossing of effects at some point. Understanding the background research on the root causes of mental illnesses and drug dependence helps develop prevention and treatment options for both conditions. Below are some of the speculations made as to why mental illness and drug addiction coexist;

Identical neurobiological origins for both conditions

Psychoactive drugs may help mitigate some of the mental illness symptoms, or they are used to counteract the side effects of the prescription drugs used to treat the mental health condition.

Substance use may hasten the occurrence of the mental condition or trigger biological alterations that appear similar to mental illnesses.

All the speculations above have evidence to back them up. It is a cause for fascination when you consider that most psychoactive drugs produce effects that lean towards psychiatric-like conditions. An example is cocaine and amphetamines, which have psychotic-related signs and symptoms. Hallucinogenic compounds like PCP and LSD cause hallucinations/delusions, which are derivatives of psychosis. 

In addition, psychoactive drugs are known to alter a user’s moods, resulting in either happiness and euphoria or depressive symptoms that are most intense during withdrawal. The psychoactive drugs also interfere with cognitive functioning, which is characteristic of mental illnesses. All these examples expose the commonality in neurobiological origins for substance dependence and mental illness. 

According to several studies, more than half of all individuals with a mental illness also have a substance dependence problem. This is in comparison to 6 percent of the general United States population. Statistically speaking, persons with a mental disorder are 4.5 times more prone to substance abuse than those without any mental disorder. From these, we can clearly see how these two conditions overlap each other.

Prevention and treatment of psychoactive drugs dependence 

Advanced neuroscientific research has led to the development of a myriad of pharmaceutical and behavioral options that can be used to prevent and treat substance dependence. While many have successfully shown a positive impact on an individual’s lives, many of these treatment options have raised numerous ethical questions.

As long as the research is ongoing, we can only expect more improved and effective treatments to hit the market. The singular question remains, how can we define ‘successful treatment’? is it a success only if the drug user completely abstains from the substance or is it still a win if the treatment leads to the reduced intake of the drug, reduction of frequency, or the safe intake of the drug? Below is a table illustrating the different types of pharmacological therapies available for the prevention and treatment of substance dependence.

AlcoholAcamprosate is a synthetic substance with structural similarity to a naturally occurring amino acid. Restores the normal activity of neurons, which become hyperexcited as a result of chronic exposure to alcohol.Overall, patients treated with acamprosate exhibit a significant increase in rate of completion of treatment, time to first drink, abstinence rate and/or cumulative duration of abstinence, compared with patients treated with placebo.
Naltrexone: Blocks opioid receptors.Naltrexone is effective in reducing relapse and in helping people to remain abstinent and to decrease alcohol consumption.
Disulfiram interferes with the normal metabolism of acetyaldehyde, a metabolite of alcohol. High acetaldehyde levels produce an unpleasant reaction that is intended to render the consumption of alcohol aversive.The efficacy of disulfiram is variable, and is confounded by the need to carefully titrate the dose, and by the need for a high degree of compliance.
NicotineNicotine substitution with nicotine patch or gum.All nicotine-replacement therapies are equally effective in helping people to quit smoking, and, combined with increased public service announcements in the media about the dangers of smoking, have produced a marked increase in successful quitting
Bupropion: A weak norepinephrine and dopamine reuptake inhibitor, and a nicotinic receptor blocker.Bupropion improves the abstinence rates of smokers, especially if combined with nicotine replacement therapy .
Immunotherapy: Vaccines that can prevent nicotine from acting on the brain have been proposed.Vaccines are not yet ready for clinical trials. Trials with mice show promising results.
HeroinMethadone (synthetic opioid agonist).Methadone maintenance treatment is safe, and very effective in helping people to stop taking heroin, especially when combined with behavioural therapies or counseling and other supportive services.
Buprenorphine: Partial agonist at the mu opioid receptor and a weak antagonist at the kappa opioid receptor.Relatively long duration of action and good safety profile.
Levo-alpha-acetyl-methadol (LAAM): a synthetic opioid.Long-acting synthetic opioid that can be used to treat heroin dependence, but it needs only be taken three times per week, thus making it even easier for people to use this therapy.
Naltrexone blocks the effects of morphine, heroin and other opioids by acting as antagonist at the opioid receptors.This therapy begins after medically supervised detoxification, because naltrexone does not protect against the effects of withdrawal, and can in fact precipitate withdrawal symptoms in dependent people. Naltrexone itself has no subjective effects or potential for the development of dependence. Patient noncompliance is a common problem. Therefore, a favorable treatment outcome requires that there also be a positive therapeutic relationship, effective counselling or therapy, and careful monitoring of medication compliance.
CocaineGBR 12909 is an inhibitor of dopamine uptake that antagonizes the effects of cocaine on mesolimbic dopamine neurons in rats, and blocks self-administration of cocaine in rhesus monkeys.Clinical trials of this substance were at the planning stage in 2004.
Immunotherapies: cocaine is sequestered in the bloodstream by cocaine specific antibodies that prevent its entry into the brain.Clinical trials are underway.
Sedatives/hypnoticsSlow tapering of substance dose combined with behavioral therapy.Effective.

Behavioral therapies used to treat drug addiction

Behavioral therapies are also used in the management and treatment of substance dependence. Most of these therapies try to relate to the learning and motivation processes we talked about earlier.

For example, motivational and cognitive therapies aim at substituting the motivation to indulge in psychoactive drugs to other positive actions and behaviors. Contingency therapy management leans towards positive reinforcement and punishment for behavioral management.

These tactics are used to try and ‘unteach or unlearn’ the behavior of dependency. In short, the same methods used in developing substance dependence are the same as those used to overcome the dependence. Check out the table below for a summary of the behavioral therapies used to combat substance dependence.

Cognitive behavioural therapiesCognitive behavioural therapies focus on:(a) altering the cognitive processes that lead to maladaptive behaviours of substance users;(b) intervening in the behavioural chain of events that lead to substance use;(c) helping patients deal successfully with acute or chronic substance craving;(d) promoting and reinforcing the development of social skills and behaviours compatible with remaining substance free.The foundation of cognitive therapy is the belief that by identifying and subsequently modifying maladaptive thinking patterns, patients can reduce or eliminate negative feelings and behaviour (e.g. substance use) 
Relapse preventionAn approach to treatment in which cognitive behavioural techniques are used in an attempt to help patients develop greater self-control in order to avoid relapse. Specific relapse prevention strategies include discussing ambivalence, identifying emotional and environmental triggers of craving and substance use, and developing and reviewing specific coping strategies to deal with internal or external stressors 
Contingency managementA behavioural treatment based on the use of predetermined positive or negative consequences to reward abstinence or to punish (and thus deter) substance-related behaviours. Rewards have included vouchers awarded for producing substance-free urine samples that can be exchanged for mutually agreed upon items (e.g. cinema tickets) and community reinforcement in which family members or peers reinforce behaviours that demonstrate or facilitate abstinence (e.g. participation in positive activities). Negative consequences for returning to substance use may include notification of courts, employers, or family members 
Motivational enhancement therapyThis brief treatment modality is characterized by an empathetic approach in which the therapist helps to motivate the patient by asking about the pros and cons of specific behaviours; by exploring the patient’s goals and associated ambivalence about reaching these goals; and by listening reflectively. Motivational enhancement therapy has demonstrated substantial efficacy in the treatment of substance dependence.” 


A significant amount of the GBD and disability can be linked to the use of psychoactive drugs. Consequently, drug dependence is the major contributor to burden linked to substance use, with tobacco and alcohol taking the lead as the major contributors to the global burden. Following the severity of this information, it is prudent to curb the use of these licit and illicit drugs in order to promote global health. There is a growing need to come up with stringent health policies to fight off substance use and dependence.

Through the use of reliable scientific research gathered from numerous neuroscientific studies, leaders and other people in positions of power and great influence can push for the implementation of policies that will help reduce the burden of disease and disability caused by substance use. Below are some recommendations that can be used to foster openness and consequently lead to positive action and reforms.

  • All psychoactive substances can be harmful to health, depending on how they are taken, in which amounts and how frequently. The harm differs between substances and the public health response to substance use should be proportional to the health-related harm that they cause
  • Use of psychoactive substances is to be expected because of their pleasurable effects as well as peer pressure and the social context of their use. Experimentation does not necessarily lead to dependence but the greater the frequency and amount of substance used, the higher the risk of becoming dependent.
  • Harm to society is not only caused by individuals with substance dependence. Significant harm also comes from non-dependent individuals, stemming from acute intoxication and overdoses, and from the form of administration (e.g. through unsafe injections). There are, however, effective public health policies and programs which can be implemented and which will lead to a significant reduction in the overall burden related to substance use.
  • Substance dependence is a complex disorder with biological mechanisms affecting the brain and its capacity to control substance use. It is not only determined by biological and genetic factors, but psychological, social, cultural and environmental factors as well. Currently, there are no means of identifying those who will become dependent – either before or after they start using drugs.
  • Substance dependence is not a failure of will or of strength of character but a medical disorder that could affect any human being. Dependence is a chronic and relapsing disorder, often co-occurring with other physical and mental conditions.
  • There is significant comorbidity of substance dependence with various other mental illnesses; assessment, treatment and research would be most effective if an integrated approach were adopted. Treatment and prevention insights from other mental illnesses or substance dependence can be used to inform treatment and prevention strategies in the domain of the other. Attention to comorbidity of substance use disorders and other mental disorders is thus required as an element of good practice in treating or intervening in either mental illness or substance dependence.
  • Treatment for substance dependence is not only aimed at stopping drug use – it is a therapeutic process that involves behaviour changes, psychosocial interventions and often, the use of substitute psychotropic drugs. Dependence can be treated and managed cost-effectively, saving lives, improving the health of affected individuals and their families, and reducing costs to society.
  • Treatment must be accessible to all in need. Effective interventions exist and can be integrated into health systems, including primary health care. The health care sector needs to provide the most cost-effective treatments.
  • One of the main barriers to treatment and care of people with substance dependence and related problems is the stigma and discrimination against them. Regardless of the level of substance use and which substance an individual takes, they have the same rights to health, education, work opportunities and reintegration into society, as does any other individual.
  • Investments in neuroscience research must continue and expand to include investments in social science, prevention, treatment and policy research. The reduction in the burden from substance use and related disorders must rely on evidence-based policies and programs which are the result of research and its application

Lastly, there are numerous ethical issues facing the various developing technologies and therapies that are used in the treatment of substance dependence and various other related conditions. We call upon the national and international scientific policy communities to address these issues as a priority, so that the individuals seeking treatment can get access to the best and most effective services.


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