The Science Behind Co-occurring Drug Use and Mental Health Disorders

How Can Drug Abuse Lead To The Development Of Mental Disorders That Were Not Present Prior To Consumption?

Abstract

Scientists and psychologists have both conducted substantial research on the relationship that exists between mental health and substance usage. However, these connections are so complex that it is frequently difficult to determine if a person's mental health problems are a result of drug misuse or whether they were present before. To raise awareness of the terrible effects of drug usage on the brain, this paper explains the pathology of how addiction to some of the most common illicit substances, specifically opioids, amphetamine, LSD and ketamine, can result in the development of mental disease. These drugs all fall under different categories of pharmaceuticals yet share the similarity of contributing to mental unwellness amongst individuals, highlighting the need of new methods to combat illicit drug abuse amongst the population.

Illicit Drugs Effects On The Brain:

The term “illicit drugs” refers to drugs that are illegal to process, sell and consume with little to no medical uses. Examples include heroin, cocaine, meth, ecstasy, and LSD. They can be naturally grown such as cannabis and marijuana, or entirely synthetic. These drugs are further divided into several different classifications, depending on their effects on the brain: Stimulants, Depressants, Narcotics, and Hallucinogens.

Due to their varying effects on the central nervous system, these drugs, depending on their classification, impact the human brain in different ways. However, scientists have reached a general consensus that drug use permanently alters the CNS (central nervous system) by disrupting normal communication between chemical messengers and neurotransmitters. Occasionally, these drugs can also induce symptoms of intoxication and withdrawal that mimic mental disorders, referred to as “Substance induced mental disorders”, which are often reversible with abstinence from the drug.

Stimulant Drugs Relationship To Mental Health:

Introduction:

Regular use of stimulants have been linked as a risk of inducing acute and chronic psychosis, along with schizophrenia. The majority of stimulants are not only known to manipulate neurotransmitter levels but monoamine transmission. Monoamines include substances such as dopamine, serotonin and norepinephrine, all essential to the reward, pain and temperature pathways throughout the human body. Stimulants either block the reuptake of these chemical messengers, prolonging their stay in neurons, or stimulate an influx of the transmitters, thereby increasing their activity within the brain's circuitry.

The mesocortical, mesolimbic, and nigrostriatal pathways are altered by the consumption of stimulants, each of which are associated with different segments of our personality and actions. The mesocortical pathway is connected to cognitive functions, most notably working memory. The mesolimbic pathway is associated with reward processing, emotional responses, and the development of behavioral patterns. Finally the nigrostriatal pathway works to produce movement to gain awards, therefore leading to the development of habits. When these pathways are altered, a person's conduct, emotional responses, personality, and interpretation of reality may be severely influenced, leading to symptoms of what psychologists interpret as psychosis and schizophrenia.

Amphetamines Connection To Mental Health:

The stimulants amphetamines and methamphetamines specifically have a reputation for contributing to the development of these mental disorders amongst drug abusers. The first association between amphetamine and the psychiatric disorder of psychosis sprouted from studies conducted in the 1960s and 70s, where healthy volunteers were exposed to relatively high doses of amphetamine and in response developed psychotic symptoms. Furthermore, recreational amphetamine increases the risk of developing symptoms of psychosis. Among chronic methamphetamine users, high levels of use in the previous month have been shown to be associated with up to five times increased risk compared to non-users. The most common symptoms are persecutory delusion and auditory hallucinations. There are conflicting results of studies debating whether there is a dose-response relationship between psychosis symptoms and the amount of amphetamines administered in laboratory investigations.

Psychosis may be precipitated by amphetamine use due to its effects on dopaminergic activity in the central nervous system. Amphetamine activates receptors in the brain and increases the activity of a number of neurotransmitters, specifically norepinephrine and dopamine. These transmitters are both associated with feelings of pleasure and satisfaction. Psychosis is a mental disorder characterized as a disconnect from reality and neurotransmitters are the brain's main form of communication, as they are constantly transmitting information from 1 neuron to another. It’s associated with how we feel and how we react to situations and conflict. The dysregulation of neurotransmitters in the brain likely causes feelings of panic, confusion, disarray and stress, leading to a person mimicking the symptoms of someone suffering from psychosis. Moreover, people with schizophrenia have an overactive dopamine system, releasing more dopamine than normal, healthy individuals, once again linking the mental condition with amphetamine abuse.

Other stimulants such as Tobacco are also known to contribute to the development of psychosis and schizophrenia amongst long time drug abusers.

Depressants Linkage To Mental Health:

Introduction:

Depressants are nearly the direct opposite of stimulants, as indicated by their namesakes. As opposed to stimulating brain activity, depressants increase the activity of GABA, a chemical known to slow down brain functions. Drugs under this category reduce arousal and stimulation while slowing down messages between the CNS system and the rest of the human body. Depressants include drugs such as alcohol, opioids, GHB, and rohypnol. Despite narcotics being considered their own drug category, all narcotics are classified as depressants. Narcotics are drugs used to treat severe pain, induce drowsiness, and can also be used as anesthesia. They are now recognized under a different name, opioids.

There is an abundant amount of research suggesting that opioid use can be linked to depression and anxiety disorders, due to the fundamental changes that occur in the brain when the drugs are used. Furthermore, there is a prevalent trend in studies centered around the depressant, stating that prolonged usage of opioids is a higher risk factor for developing depression when compared to simply consuming high doses.

Opioids have one of the longest histories of drug abuse in human society along with tobacco, largely due to its main natural alkaloid constituents (i.e., natural opiates). Opiates are a broad category of organic or semi-organic compounds that bind to the mu, kappa, and delta opioid receptors in the body and have pharmacological effects similar to that of morphine. Heroin is one of the most commonly consumed opiates in the world. The term opioids refers to related chemical substances (drugs) that interact with opioid receptors on nerve cells in the body as well, albeit some are produced synthetically whereas opiates are naturally occuring. Both opioids and opiates disrupt the natural production of norepinephrine in the central nervous system, thus blocking pain messages from being sent to the brain. They also reduce body temperature, lower drowsiness, and slow heart rate, blood pressure, and respiratory functions. Repeated exposure to escalating doses of opioids alters the brain to the point where it functions more or less normally when opioids are consumed, and abnormally when they are not.

Opioid Linkage To Mental Health Disorders:

These effects of opioids are considered the primary reason as to why prolonged usage may lead to the development of depression (a mood disorder that causes a persistent feeling of sadness and disinterest) along with anxiety. As mentioned previously, opioids attach to opioid receptors which are located in areas of the brain known as the reward pathway, which includes the cerebral cortex, the nucleus accumbens, etc. It begins in the ventral tegmental area, where neurons release dopamine causing you to feel sensations of pleasure and satisfaction. Eventually the brain makes a connection between the activity and the sensation ensuring the repetition of that behavior. These receptors are also located amongst the pain pathways in the brain, including the brain stem, spinal cord, thalamus etc. There are two separate pathways in which information can be delivered, the lateral spinothalamic tract, which focuses on the transmission of pain and temperature sensation, and the anterior spinothalamic tract, which carries info relating to crude touch and firm pressure sensation. Certain opioids are more susceptible to binding with certain receptors, amongst these pathways.

Heroin is an opioid that binds to specific receptors throughout the body, which triggers a series of chemical changes within and between neurons, leading to feelings of pleasure and pain release. The feeling produced from these changes is almost euphoric, making someone extremely susceptible to develop a dependency for the substance. As a result of encountering constant external opioids, the brain will naturally produce less of its own naturally occurring substances, thus resulting in the loss of dopamine and serotonin production in the brain. The lack of neurotransmitters to produce positive feelings of satisfaction results in withdrawal symptoms mimicking that of depression. The reversibility of these effects depend on how long the misuse of heroin went on. Furthermore, using heroin for prolonged periods of time causes harmful proteins to build up and become hyperphosphorylated, specifically the TAU protein. Furthermore, heroin use leads to inflammation of the brain, thereby causing structural changes similar to those associated with Alzheimer's disease. When this happens, symptoms such as depression, paranoia, nervousness, and personality changes occur.

General Effects Of Depressants On The Brain:

Long term use of Opioids can change the physical structure of your brain, causing neurological and hormonal systems to be out of balance. Reduced sex hormones are a common feature of chronic opioid use and can cause fatigue, depression, loss of muscle mass and osteoporosis. Furthermore, long term use of depressants can also lead to decreased white matter in the brain. White matter protects the nerve fibers of the brain and helps signals travel quickly between different parts of the brain. This makes it more difficult for the user to control impulses, make decisions and cope with difficult situations. It can also affect an individual's ability to think quickly and clearly, therefore having a profoundly negative impact on an individual's life. These changes in cognitive thinking can all lead to the development of depression and anxiety, as they can completely alter the brain and behavior patterns.

Hallucinogens:

Introduction:

Hallucinogens are a diverse group of psychoactive drugs that alter perception, thoughts, emotions, and senses. They are known to provide extreme distortions of reality to users. Also known as psychedelics, they work by disrupting how neurotransmitters work in the brain, as do all drugs. They can be divided into two different categories, classic hallucinogens and dissociative drugs.

Classic Hallucinogens:

All classic hallucinogens are thought to stimulate a specific serotonin receptor subtype that is expressed on neurons in the brain. It has been proven that this receptor is central to the action of hallucinogens in the brain as its inhibition abolishes all effects of psychedelics throughout the body. The affinity of different types of hallucinogens to the serotonin 2a receptor, also correlates directly with the strength of the psychedelic. For example, LSD has an extreme affinity for the 2a serotonin receptor and is a remarkably potent drug. Classic hallucinogens stimulate the 2a receptor by binding to it, thus mimicking the actions of serotonin throughout the brain. In order to successfully bind, the drug must first alter the receptors' conformation or ‘shape’, and ultimately alter the internal behavior and conditions the neuron operates under. For serotonin 2a, this mainly involves increasing the excitability of the hosting brain cell. Serotonin 2a receptors are most commonly found on pyramidal neurons, neurons with a pyramidal shaped soma (cell body) and two dendrites.

Dissociative Drugs:

Dissociative drugs cause feelings of being dissociated from reality. They often cause distortions of time, space, and one’s own body, and often lead to feelings of panic and confusion. According to the National Institute on Drug Abuse, laboratory studies suggest that dissociative drugs “cause their effects by disrupting the actions of the brain chemical glutamate at certain types of receptors—called N-methyl-D-aspartate—on nerve cells throughout the brain.” Glutamate is an important neurotransmitter that plays a role in cognitive function and shaping learning and memory. It also influences the perception of pain along with emotion. By disrupting communication between neurotransmitter systems throughout the CNS system that regulate sensory and pain perception, feelings of euphoria are often an after effect of dissociative drug abuse.

Dissociative and Classic Hallucinogens Connection To Mental Health:

LSD is one of the most common classic hallucinogens to be abused, maintaining a particular popularity in the United States. It acts on a number of neurotransmitter receptors, including dopamine and serotonin. Although LSD’s physical effects are rather minor in comparison to other drugs, due to having subsidiary toxicity levels, it still has serious cognitive effects on those who use it. For example, HPPD (Hallucinogen Persisting Perception Disorder), occasionally referred to as “flashbacks” is a condition unique to psychedelics, where damages to cognitive function and perceptual changes can last anywhere from months to years following the use of LSD. The first documented case of HPPD was in 1954, and continued research in the condition indicates that hallucinogens may trigger long-term brain changes.

PCP (phencyclidine) is a dissociative drug that alters how the brain responds to serotonin, and often gives a false sense of security and safety to those who use it for recreational purposes. These cognitive effects often lead to dangerous, risk taking behaviors, particularly in young adults. It inhibits the reuptake of dopamine, norepinephrine and serotonin, and also inhibits the action of glutamate by blocking NMDA receptors. Although PCP is classified as a hallucinogen, it can also act as a stimulant and depressant in certain cases. People who suffer from addiction to phencyclidine also suffer from changes made to their brain structure, leading to memory problems, issues with concentration and perception, along with difficulty in judgment. Long time abusers may also suffer from auditory and visual hallucinations long after detoxing from the drug. These effects all lead to the development of PCP induced psychosis, where they have lost contact with reality and are having abnormal thoughts and actions.

Concluding Statement-

Although there are many different categories and types of drugs, nearly all can lead to the development of either physical or psychiatric disorders. This paper highlights a common misconception that all mental health issues in individuals existed prior to drug usage, whereas in many cases the structural changes caused by significant drug abuse lead to the development of mental disorders. It also highlights a need to further research in the psychological and neurological aspects of drug abuse, as there are too many gray areas to fully elucidate the effects of drugs on the human brain.

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Citation:

(Cover Image Source: healthline.com)

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