The Impact Of Drugs On Cognitive Functioning


23 Mar 2015

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The various effects of substance abuse on the central nervous system can now be seen with a variety of brain imaging scans. These imaging devices allow us to see changes at the molecular level immediately after drug use and grant us the ability to keep track of neurological changes over the course of the disease. As we come to understand what specific drugs do to the human brain, we will be better able to predict its course and aid the patient in the recovery process.

Drug abuse and dependence quickly develop behavioral problems in users (Devlin, 2008). Psychosocial problems arise from the behavioral issues associated with drug dependence. Most notably, and of great concern to psychologists, is that individuals who abuse drugs, quickly begin to isolate themselves from others. This isolation makes identifying the problem much more difficult, and makes the withdrawal and recovery process more difficult and painful for the user. 'Drug abuse' refers to illegal street drugs, prescription medications, alcohol, inhalants, or any substance that an individual uses to get 'high'.

Many drugs are injected intravenously for a faster 'high' and more extreme 'peak' for the user. The drugs themselves may have the major effect of impairment of mental function, but the route of administration can have serious complications as well. Persons with a history of intravenous drug abuse also are more likely to have tuberculosis of the lungs. The drug heroin can produce a nephropathy in the kidney that resembles glomerulosclerosis when the drug is used intravenously (Devlin, 2008).

Opiates ('painkillers', eg. Vicodin) by themselves have minimal pathologic effects. However, higher doses of more powerful opiates can lead to respiratory depression and death (albeit rare) (Devlin, 2008). Patients who use their analgesics as prescribed typically do not become addicted, but unfortunately tolerance may develop over time, requiring higher doses to maintain analgesia (or switch to morphine, a drug that is as powerful as it is dangerous). The problem with opiates are the not pathologic effects, but issues that rise within the interpersonal sphere. Opiate addicts invariably become more and more isolated and desire contact with others, less and less. This alienation exacerbates their already existing physical and emotional pain, and when a traumatic event hits the user, they have no one (in their mind) that they can turn to.

Cocaine use can exert a variety of negative side effects. The major acute effects producing pathologic conditions result from the increased circulating catecholamine levels with cocaine use. These increased catecholamines can produce vasoconstriction. The blood vessels become so narrow, they are vulnerable to a host of life-threatening medical disorders. The lesions can include acute hemorrhages and infarction in the brain, which can lead to death. Combining cocaine use with ethanol use can compound the damage to the heart and brain.(Awtry and Philippides, 2010).

A Brain Hemorrhage Caused by Heavy Cocaine Use

Pregnant mothers who use cocaine can affect their fetuses from abnormalities of placental function leading to low birth weight babies or an increased risk for placental abruption. Maternal cocaine use increases the risk for an accidental spontaneous abortion (Kuczkowski, 2007). This can cause a major depressive episode for the mother. During this time of depression the individual is at a high risk for increased cocaine abuse, combining other drugs looking for a better 'high', and suicide (Kuczkowski, 2007).

Amphetamines damage both the serotonergic and dopaminergic systems of the central nervous system. Alterations of the dopaminergic system may persist even after years of abstinence from use of methamphetamine and is associated with deficits in motor and cognitive performance (Gouzoulis-Mayfrank and Daumann, 2009). The damage caused to the dopaminergic system is often irreversible and makes recovery painful and extremely challenging. Even after the difficult withdrawal and abstinence from amphetamines, happiness remains elusive for years, and in some cases, for the rest of their life. SSRIs and other pharmacological treatments do little to comfort the patient.

CNS toxicity of methamphetamine may be the result of both hyperthermia as well as direct effects upon individual cells. A dose-related increase in body temperature occurs with acute ingestion of methamphetamine. This can create negative effects of methamphetamine upon the blood-brain barrier and upon neurons, leading to edema (Kiyatkin and Sharma, 2009). The damage to the blood-brain barrier makes any psychotropic drug more dangerous. The damage to the blood-brain barrier can be recovered from however, if abstinence is maintained for a number of years (Gouzoulis-Mayfrank and Daumann, 2009).

Gamma-hydroxybutyrate (GHB) is a metabolite of the neurotransmitter gamma aminobutyric acid (GABA) and also functions as a neurotransmitter by affecting the dopaminergic system. GHB may also potentiate the effects of endogenous or exogenous opiates. GHB was introduced into the U.S. in 1990 as a purported stimulant to muscle growth during sleep, but it was soon banned because of problems with overdose and adverse reactions.

There are a multitude of adverse effects that can occur within 15 minutes to an hour after ingesting GHB, including: hallucinations, loss of peripheral vision, nystagmus, hypoventilation, cardiac dysrhythmias, seizures, and short-term coma. These problems generally subside in 2 hours to 4 days. It is difficult to predict how much GHB will produce an overdose. Withdrawal from GHB can have an onset in only 12 hours and last up to 12 days after a single use! In rare instances, deaths have occurred from these adverse effects (Timby et al, 2000). Despite this evidence of rapid addiction and physical problems caused by the drug, it is a commonly abused drug in colleges across the nation to this very day. Because GHB is a liquid, and relatively easy to obtain on campus, it is suspected in countless cases of 'date rape'.

MDMA (Methylenedioxymethamphetamine; typically called Ecstasy) is an entactogenic drug of the phenethylamine and amphetamine families. In the 1970s MDMA was known as "empathy" or "Adam". Initially this drug was used to help aid couples with intimacy problems. MDMA users not only experience a general well-being 'high', but often find themselves becoming intimate with others during the 'high'.

MDMA experimentally causes selective and persistent lesions of central serotonergic nerve terminals. MDMA users can have residual alterations of serotonergic transmission, and though at least partial recovery may occur after long-term abstinence, problems may persist even after longer periods of abstinence. Long term use may be accompanied by long-lasting brain damage and memory impairment (Carter et al, 2000) (McQuire, 2000).

In the 1990s a handful teenagers that regularly went to 'raves' (all night parties) while high on MDMA, inadvertently brought ecstasy into the media spotlight. After a year of heavy use, these individuals began to show rapid intellectual decline. There was a lot confusion and myth that was caused by a widely published study that 'MDMA created holes in the brain of these teenagers'. Although this was often interpreted to mean a physical hole, the 'hole' being referred to was a lack of neural activity shown on the MRI scans. Depending on where the 'hole' existed, marked cognitive decline was shown in behavior related to the effected lobe. When the inferior frontal gyrus was damaged from MDMA, then the user had difficulty speaking, and sometimes even difficulty comprehending formerly known language.

A syndrome including hyperthermia and renal failure has also been reported with MDMA use, findings similar to the excited delirium of cocaine use. While the user's brain is being 'cooked' from the hyperthermia, the individual often just feels (and appears) a little sweaty. Because MDMA is often used at parties where everyone is high, often no one notices unless the user overdoses and passes out. In addition, persons using MDMA may experience rapid liver failure that can occur days to weeks after the drug was used (Scully et al, 2001).

The neurological effects of drug abuse are now being longitudinally studied with MRI, SPECT, and a host of other imagining software. SPECT scans have demonstrated a number of common abnormalities in substance abusers in brain areas known to be involved in behavior, such as the frontal and temporal lobes. There are some SPECT similarities and differences between the damage we see caused by the different substances that are abused.

There appears to be several similarities seen among classes of abused drugs. The most common similarity among drug and alcohol abusers is that the brain has an overall toxic appearance. In general, the SPECT scan studies look less active, more shriveled, and overall less healthy. Scalloping is a rough sea-like look on the brain's surface that is seen in long-term drug abusers . This pattern is also seen in patients exposed to toxic fumes or oxygen deprivation.

SPECT can be helpful in evaluating the effects of drugs and alcohol on the brain. On 3D surface brain images, several substances of abuse appear to show consistent patterns. For example, cocaine and methamphetamine abuse appear as multiple small holes across the cortical surface; heroin abuse appears as marked decreased activity across the whole cortical surface; heavy marijuana abuse shows decreased activity in the temporal lobes bilaterally and heavy alcohol abuse shows marked decreased activity throughout the brain. Fortunately these anomalies tend to improve with abstinence, although long term use has been associated with continued intellectual deficits seen years after abstinence.

The new clearer brain imaging techniques are helpful in several ways regarding drug and alcohol abuse. First, 3D surface SPECT brain images of drug and alcohol abusers can be used in drug prevention education. Second, SPECT studies can help break though the denial that often accompanies substance abuse. When one is faced with the abnormal appearance of their brain it is harder to remain in denial. Third, SPECT can help evaluate if there is an underlying neuropsychiatric condition that needs treatment, which in some cases lead to self-medicating. If the condition is effectively treated, then the likelihood of the user's recovery is much greater.

In American culture, the public's opinion of marijuana has been changing from one extreme to another for almost a hundred years. Now the arguments have been somewhat silenced because of the scientific evidence known about marijuana use. On average, marijuana contains approximately 400 carcinogens (cancer causing agents). When compared to tobacco's approximately 350 carcinogens, one can see how unhealthy marijuana truly is. It has been most associated with neck cancer, but the experimental study of this drug has been difficult. Although marijuana is not physically addicting, it is without a doubt psychologically addicting.

In the following SPECT scans, you can see that marijuana can not only cause cancer, but has a negative cognitive effect on users, most notably on frequent marijuana users. The effects of smoking marijuana typically cause decreased activity in the posterior temporal lobes bilaterally. The damage can be mild to severe, depending on how long a person used, how much use occurred, and what other substances were use during the same time period. Like many neurological problems, it now appears that certain individuals have a predisposition to receive brain damage from smoking marijuana (even if they are a light user).

Steady Marijuana Use

3 year history of 4x weekly use

Decreased PFC and temporal lobe activity

2 year history of daily abuse

decreased prefrontal and temporal lobe

12 Years of Daily Use

Decreased PFC and Temporal Lobe Activity

10 Years of weekend use

Decreased PFC and temporal lobe

Off and On Marijuana Use


Decreased PFC and temporal lobe activity


Severe Overall Decreased activity


Increased deep left temporal lobe activity


Overall calming of activity


Patchy increased uptake


Overall calming of activity

The pictures above with heavy marijuana usage shows overall decreased activity of the entire brain, especially in the prefrontal cortex and temporal lobes. This damage causes the user to have problems holding their attention on a given task, even tasks they enjoy. The user's memory is also negatively effected by the damage to the prefrontal cortex. People have often joked about a 'stoners' bad memory, and this is now empirically proven. Although many individuals believe only short-term memory is effected, this is certainly not the case. Events that take place while an individual is 'high' are usually more difficult to remember, and sometimes are completely forgotten. Another major problem with marijuana use, concerns its amotivational effects. Marijuana smokers become more and more lazy as frequency of use elevates. There are exceptions to this, but rarely with heavy users. The negative effects on an individual's intrinsic motivation, is most notable with daily abuse. It appears memory is the first cognitive component effected, followed by global attention problems, and eventually self-motivation becomes difficult for the addict.

These problems are of enough significance to be noticed by individuals that knew the user before marijuana use began. The overall mental decline is insidious, therefore the user rarely seeks help. Unlike heroin, cocaine, and methamphetamine, individuals that use marijuana typically do not see their habit as particularly dangerous. Most marijuana users choose friends that also get high. They often smoke the marijuana in small groups and in homes that are 'pot' friendly. This further solidifies their belief (or more likely, their rationalization) that marijuana is not harmful. So the longer they use, the more and more their circle of friends and social support become intertwined with marijuana. This pattern makes the user extremely unlikely to seek help for their addiction...unless they find themselves in legal trouble. Making the American public aware of the empirical evidence regarding the harmful effects of marijuana is necessary to eliminate the mis-information that both pro and anti-marijuana organizations have spread for decades.

The following are some high resolution SPECT images obtained from drug abusers compared to a normal brain. As I mentioned before, the addicted brain produces images that are shockingly similar to individuals that have been deprived of oxygen or exposed to dangerous toxins.

A brain that is functioning properly produces smooth/gradual changes in color on the SPECT images and contains no spaces. Abrupt changes in color and the 'holes' indicate decreased overall neural activity in that region.

Normal Brain Activity (Above)

Heroin & Methadone Use (Below)

25 years of frequent heroin use

Marked overall decreased activity

47 years on methadone

after 10 years of heroin

Marked decreased overall activity

Cocaine & Methamphetamine

28 years frequent meth use

multiple holes across cortical surface

2 years history of frequent cocaine use

Multiple holes across cortical surface

8 years of heavy meth use

marked overall decreased activity

10 years of frequent meth use

Multiple holes across cortical surface

17 years of heavy alcohol weekend use

marked overall decreased activity

22 Years of Daily Alcohol Abuse

18 years of daily alcohol use

Marked overall decreased activity

25 years of daily alcohol abuse

Marked overall decreased activity

Thankfully, recent SPECT imaging studies have discovered some good news for the addict in recovery. The following images show the toxic looking brain effected by drugs, and the same brain a year later after the patient was able to stay 'clean' from drugs. A noticeable improvement can been seen in neurological functioning after 1 year of abstinence for both alcohol and substance abusers. The brain is miraculously able to recover from some of the neural damage.

1 Year of Sobriety SPECT Comparisons

During substance abuse

One year drug free

During Substance Abuse

One year drug free

However, this evidence does not suggest that the user in recovery will feel completely heal emotionally. Evidence has yet to be found that the brain is capable of recovering from extreme levels of dopamine and serotonin In individuals that abuse drugs that effect the user's dopamine receptors (eg., opiates, amphetamines) the addict struggles with regulating their emotions for the rest of their life. Specifically, the ability to maintain a positive mood, is slow to recover from the drug abuse. This occurs because the brain learns to adjust to the high levels of dopamine (and likely serotonin) that are extremely elevated during the drug's 'high' peak points. The brain perceives 'joy' or 'happiness' when levels are above the baseline of neurotransmitter activity. Achieving a level of neurotransmitter activity required to be above this new standard, is quite difficult. Sadly, in many cases of long term drug abuse (especially heroin and methamphetamine), the recovering addict reports never again truly feeling the level of happiness they use to experience naturally. Currently researchers are searching for a way to assist the brain in responding to the natural levels of neurotransmitters that were skewed with drugs. This would be an invaluable tool for individuals trying to recover from long-term drug abuse.


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