The Effects of Cannabis on Health and Personality. A Study

Master's Thesis, 2015

41 Pages, Grade: B-


Table of Contents


2.1 Substance use among adolescents
2.2 Medical use of cannabis
2.3 Depression & Anxiety related to cannabis
2.4 Negative childhood experiences and cannabis
2.5 Antisocial and other problematic attitudes/behaviour
2.6 Perception problems
2.7 Reducing cannabis use
2.8 Gender differences on cannabis addiction



5.1Plan of investigation
5.2 Sample
5.3 Ethical Considerations
5.4 Procedure\ Statistical Analysis
5.5 Questionnaire Design

6.1 Participants’ Characteristics
6.2 Descriptive Statistics

7.1 Results’ Interpretation

8.1Summary of the study
8.2 Limitations



Recent research has elucidated a number of important interrogations concerning cannabis’ adverse effects on health, mood, attitude and personality traits. As the usage of cannabis increases in many populations over the world and has shown a significant prevalence amongst young people, a debate is still pending on the possible effects of long-term and acute use.

Aims : The aim of the current paper is to discuss the negative along with positive effects of cannabis on health as well as the attitude changes of the individuals whether would be typical and ordinary or dysfunctional. The objectives of the research study are the following : (a) issues regarding its possible adverse effects on mood , (b) the therapeutic potential of cannabis, (c) check the dissimilarities on personality traits between chronic, non-chronic and non-users, (d) gender differences, (e) check on depression stages amongst all three (3) groups. Cannabis consumption can be controlled but in some cases individuals experience negative psychological and physical effects due to the fact that their habit turns into addiction. Many psychological studies linked cannabis use and schizophrenia as well as depression levels showing a weak significant association but at the time there are not strong considerable results to establish those findings.

Methods: A total of 106 participants were assessed and randomly chosen to answer the questionnaires. The study included 59 male and 47 female participants who were categorised in three main groups; the non-users, regular users and heavy users. The research questionnaire consisted of the General Coping Questionnaire, the DUDIT test and the Dysfunctional Attitude Scale.

Results: Participants who were allocated in the heavy users group scored high in negative childhood experiences and neuroticism. Regular users and heavy users were significantly less concerned about their control over cannabis use but perfectly matched on their use expectancies. Males reported results of more regular use than females but females (M=2.62 vs M=1.95) reported higher levels of addiction and heavier influence. On descriptive statistics non-users reported very high levels of approval need and success but regular users reported higher levels of vulnerability than the rest of the groups.

Conclusion: This study supports the attitude change of heavy cannabis users in a psychosocial perspective but also giving evidence that cannabis can be used for therapeutic action as it has a potential role in the treatment of convulsive disorders, neuroticism and gives assurance for future benefits in a great range of illnesses.


2.1 Substance use among adolescents:

Use of cannabis is highly common among adolescents ( Kaminer; 1999 , Myers & Waldron 1999). Among 11 year olds primary school students, 4% had used some unpredictable substances while 1% had used cannabis. A similar statistical study based on 15 year olds gave reports of 7% of children using unpredictable substances compared to 27% who had used cannabis once or still use it regularly (National Statistics UK, 2005). Nearly all cannabis users receive the drug regularly; this prevalence between adolescents carries significant risks of unfavourable consequences (Cooper, 1994; Kandel, Karus & Yamagushi 1986;). For instance, adolescent cannabis use is merely associated with body injuries, vehicle accidents, assaults and attitude changes (Brookoff , Cook, Williams & Mann 1994; Portnov, Blow & Hill; 1994). Prevention methods have to be introduced and be successful in order to prevent the unfavourable consequences which develop from the risk factors contributing to heavy and regular substance use among adolescents.

2.2 Medical use of cannabis :

Problems related to cannabis’ use still continue to be a severe cause of psychological and physical effects on health in a range of many developed and developing countries ( Ashton, 2001). However, there is a shared debate on whether cannabis possesses therapeutic ingredients and can be used in a clinical beneficial manner or whether is linked with serious illnesses and negative behavior. Previous research has emphasized the potential future benefits of cannabis since cannabinoid system has many significant similarities with the opioid system (Reynolds;1890). The best supported encouraging indication is the use of cannabis as an antiasthmatic agent in cases where a bad-tempered nervous system is involved (McMeens 1860; Waring 1874). As it concerns additional therapeutic potentials of cannabis medical use, it can be used in cases of muscle relaxation, opiate withdrawal, glaucoma as well as an analgestic, antidepressant and antiemetic medication ( Walton 1938; Marshall 1898 ;Howlett ;2002). Moderate doses of cannabis use appeared to be useful in decreasing emotional reactivity and subjective sense of pressure along with reduction in stress levels ( Walton; 1938).

A number of studies has shown a significant link between cannabis and depression, but the nature of the association is not yet clear as there are many overlapping studies (the US Epidemiological Catchment Area study (ECA), Donohue B, Acierno R, Kogan E. 1996). The literature studies suggest that cannabis use and personality traits both include risk factors for the later progression of schizophrenia. However, there are no significant results in all previous studies to establish this outcome (The Royal College of Psychiatrists, 1993). Evidence on cannabis use and misuse have shown that it’s behavioural and physical dependence can occur in approximately 10% of regular users as well as that early and regular use can be an important predictor of future dependence (Reese T. Jones, Neal Benowitz, John Bachman, 1976). The evidence indicates that chronic heavy use of cannabis carries major risks for the individual user’s health system and behaviour. Chronic use of cannabis can also induce some symptoms on a regular basis, for instance there is impairment of concentration, hard to change the behaviour, loss of interest in certain enjoyed activities plus personality changes which include poor judgement and inappropriate attitude.

Cannabidiol or cannabis can be used in medical treatment for anxiety, chronic pain or HIV pain, cancer patients, multiple sclerosis patients and nausea. Further research studies concerning cannabis medication on various psychological and biological aspects will be discussed later on in the current report. The greatest advantage of cannabis as a medicine is its unusual safety as huge doses of cannabis were given to dogs without causing death and there is no evidence that it can cause death in human beings. Moreover, there wasn’t any evidence that medical use of cannabis can lead to habitual use.

2.3 Depression & Anxiety related to cannabis:

Many people use cannabis infrequently whereas there is a another group of heavy and regular users who experience problems due to cannabis dependence. Cannabis use is mostly common in young people and so are depression, anxiety, perception deficits and affective disorders. Several studies support that alcohol and affective disorders such as depression and anxiety co occur. Approximately 80% of people who are dependent on alcohol had depression symptoms therefore there is a high association between alcohol dependence and depression disorders ( Schuckit 1985; Regier et al 1990; Roy et al 1991 ; Kessler et al 1996). However there is a question on whether cannabis dependence or use disorders can co-occur with depression, anxiety and affective disorders. Up-to-date research supports that young people who use cannabis on a regular basis can damage their embryonic brain and tend to be more vulnerable to anxiety and depression. Nevertheless, there is research supporting that cannabis can be actually used as an antidepressant in medical environments and tends to be more functional on the short-term effects than on the long-term effects (Gabriella Gobbi, 2007).

A number of studies have suggested that cannabis maybe the cause of depression or that depression may lead to cannabis use but also suggest that this association can be explained by additional factors such as the mixing of other drugs (Canon and Ratter; 1991 , Degenhardt et al; 2003). A related study supported that cannabis use at age 15 to 26 was not associated with depressive symptoms at the age of 24 to 25 but was associated with lower levels of life satisfaction (Kandel et al; 1986). In contrast, Brook et al in 2002 found that early cannabis use was associated with a small increase on the risk of depressive disorders in users by the age of 27 years old. However, there is still no evidence that cannabis use can increase the risk of depression or that depression can lead to cannabis use and even when there is some association between heavy cannabis use and depression disorders there is still no significant evidence that can be explained.

2.4 Negative childhood experiences and cannabis:

Cannabis use in young people has been linked with an increased risk of later psychosis. Nearly every research study supports that childhood traumas can cause life-long depression and anxiety as well as many emotional and psychological disturbances. Negative childhood experiences are significantly associated with both risk of psychosis and increased levels of substance misuse. In a follow up assessment concerning the association between cannabis use and psychotic symptoms depending on factors such as age, economic status, childhood experiences and gender, results have showed that individuals who used cannabis 3 or 4 times a week were 2.44 times more likely to experience psychotic symptoms than non-users and users of 3 or 4 times a month were 1.5 times more likely (Henquet et al; 2005). The occurrence of early cannabis use and negative childhood traumas can significantly increase the risk of psychotic symptoms, however cannabis itself as a factor cannot be highly linked with psychotic indications as there are no significant results in previous studies to establish this outcome. According to Harley et al in 2000 “the presence of both childhood trauma and early cannabis use significantly increase the risk for psychotic symptoms beyond the risk posed by either risk factor alone, indicating that there was a greater than additive interaction between childhood trauma and cannabis use”.

In a research study by Reigstad et al, in 2006 results gave evidence that childhood abuse is significantly linked with depression, symptoms of depression and high risk of suicidal attitude. Furthermore, a study by Houston et al, in 2008 found no significant link between early cannabis users or psychosis and childhood trauma.

2.5 Antisocial and other problematic attitudes/behaviour:

Children and adults who smoke cannabis are more likely to behave anti-socially and to have mental health problems, on the other hand cannabis can be used in order to treat depression and can lead to a more sociable attitude. Boys are twice as likely to misbehave and commit antisocial actions, such as fighting or carrying a knife; in compare to girls that use cannabis. In a study based on the personality correlates of cannabis use among youthful offenders, was found that individuals who were not cannabis users and infrequent users had more typical criminal profiles than heavy users, with the non-users being more authoritarian and less intelligent. However, regular cannabis users turned out to be the best socialized and well adjusted than the rest of the tested groups ( McGuire, Judith S, Edwin I. 1974).

2.6 Perception problems:

It has been suggested that cannabis can partially cause mental disorders including panic attacks, delusions, uncontrollable aggressiveness and a number of psychosis (Thornicroft; 1990). Cannabis use, in the short term, damages perception, thinking, judgement and memory deficits that may last for several weeks after last use.

Furthermore, suggestions had been made that the tendency in cannabis use may have more to do with changes in the perception of health risks which are associated with cannabis than changes associated with its legal status ( Single et al; 2000).

2.7 Reducing cannabis use:

An action that can be taken into account for reducing cannabis use in young healthy adults is Motivational Interviewing (Barrowclough et al; 2001). Motivational interviewing (MI) is a type of client-centred counselling approach which aims to reduce the risks related with unhealthy behaviours such as drug use in the perspective of personal goals ( Rollnick and Miller; 2002). MI approach relates to the advantages and disadvantages of an individual’s drug behaviour as viewed by themselves and aims in the progression of behavioural change (Rogers, 1967). MI can be offered in order to reduce or prevent a certain unhealthy behaviour which already harms the individuals or will more likely harm them in the future. Adolescents, have the tendency to use more than one illegal or legal drug at the same time or in a relatively short period of time, thus Motivational Interviewing (MI) which can work concurrently with the usage of multiple drugs is able to reduce cannabis in healthy young adults. (McCambridge and Strang ; 2003). Substance abuse treatment programmes have been equipped mostly to the need of male users, a suggestion by Burman in 1994 was that treatment programmes addressing the female population should emphasize on skills like problem solving, life skills, self support and assertiveness.

2.8 Gender differences on cannabis addiction ;

There is very limited data concerning cannabis effects and impact on gender differences but there are relative studies supporting that women tend to get more addictive than men. In a study concerning tobacco smoking, results had shown that women are less likely than men to quit smoking whereas in compare with men who have quitted tobacco smoking, women quitters were more likely to relapse and start smoking again (Baruch & Biener; 1987).

The present study aims to examine patterns of association between cannabis use, and depression, anxiety and control perception based on the user’s general coping at the time and negative childhood experiences.


Cannabis is the most commonly used illegal drug in Britain and it is a naturally occurring drug which can be used as a medicine in some countries. Previous studies on cannabis indicated that there is an epidemiological link between cannabis use and psychosis probably representing a causal role of cannabis in fastening the start or relapse of schizophrenia (Thornicroft, Hall et al, Tennant & Groesbeck (1990). The effects of cannabis are caused by tetrahydrocannabinol (THC) which induced both negative and positive psychological as well as physiological effects on the human body. Even though many European countries have actually legalized medical cannabis in order to eliminate symptoms which may occur in chronic illnesses (Warner et al, 1994), there are some concerns about the chronic use of cannabis for any cause. Researchers support that high consumption of cannabis can lead to an increased risk of schizophrenia and bipolar disorders but the final conclusions of the studies are very unclear on whether this is true or not. As it concerns the biological aspect, THC which is the main active ingredient in cannabis attaches to the membranes of nerve cells in the central nervous system which include protein receptors. After the attachment on the nerve cells, THC stars a chemical reaction that produces all the effects of cannabis use on the body. THC is most likely to have negative effects on the hippocampus in the brain where suppression of memory takes place.

Many studies have been based on perception problems and acute cognitive impairments of healthy individuals who are using cannabis. Difficulties with concentration, disturbances of short-term memory, dysfunctional vision, distorted time perception and sexual enhancement are some of the main areas that can be affected by the Class C illegal drug.

Research studies concerning cannabis use has shown signs of distorted flow of time and emphasized on the perception on slowing down time in several aspects ( Gautier; 1846 , Ginsberg; 1966). For instance, individuals who took part in the studies reported that they couldn’t focus on the upcoming moment because they focus mainly on the current moment (Halikas et al; 1971). Cannabis users commonly deal with distance, finding that the space between people seemed larger or that the walking distance they did was quiet different from the actual room space. This effect may be confusing due to time distortion because it can be assumed that the space distance is longer when it takes more time to travel it (Bech et al; 1973).

Although hallucinations are very infrequent, there are times when distorted visual stimuli can appear in heavy cannabis consumption. For instance an ordinary room that is well known by the user might seem darker and more strange ( Gautier; 1846 , Tart; 1971).Laboratory studies have shown evidence that cannabis use can alter the perception of short term memory such as forgetting the topic in the middle of a conversation but cannot actually affect long term memory (Tart; 1971, Adamec et al; 1976).As it concerns the link between cannabis and sexuality, regular users reported that they experience new sexual feelings as well as a notable increase in their excitement and more responsiveness to their partner. Sensitivity of touch is the most common alertness that takes place along with sexual enhancement ( Weller and Halikas, 1984).

Cannabis use can be associated with a number of brain and body illnesses as a therapeutic mean towards a healthy organism. For instance, anorexia can be found in individuals who experience an acute loss in their desire to eat and it is often associated with a number of psychological factors. Other causes which can lead a healthy individual to anorexia is the use of Class A\B illegal drugs such as cocaine or heroin, body reactions to previous medications and a variety of stomach or abdomen disorders. However, there can be many personal reasons for developing anorexia as a response, such as the standards of certain countries which represent pure “beauty” in the bodies of very thin models. In general, cannabinoids gave evidence for stimulating hunger sensation and can be used as a medical treatment for anorexia but in cases of anorexia nervosa studies have shown very small change in appetite stimulation or no effect at all as the underlying mechanism is not the loss of appetite. Synthetic THC pills known as “Marinol” are specifically designated for the treatment of anorexia disorder and can be prescript to patients with anorexia caused by cancer chemotherapy, AIDS syndrome and relevant HIV infections. A controlled study by Grotenhermen and Russo in 2002 supported that THC had an appetite-enhancing effect on AIDS patients who received daily doses of 5mg to 20mg. In comparison to placebo, THC doubled hunger sensation and AIDS patients tended to maintain a steady body weight in the period of seven months. THC also influenced body weight in patients with Alzheimer’s disease who had problems with their appetite increasing their current desire for food (Russo; 2002).

Furthermore, a research study was conducted on patients suffering from Post Traumatic Stress Disorder (PTSD) who experience regular nightmares and were currently undertaking medicinal therapy. ‘Nabilone’ is a synthetic cannabinoid with a slight modification on its molecular structure which has a therapeutic use in clinical environments as an antiemetic as well as analgesic for pain and is currently available in several countries on pharmaceutical prescription. ‘Nabilone’ was used on patients with PTSD in order to test if there is any subjective improvement concerning nightmare experience. After testing ‘nabilone’, results have shown that 72% of PTSD patients noted a significant decrease in nightmares or the termination of experiencing nightmares. Improvement was also noted in the quality of sleep and sleep time. Thus, ‘nabilone’ gave evidence for potential healthy modifications in patients suffering from Post Traumatic Stress Disorder and subsequently nightmares (Fraser; 2009).

An examination of depression, supports that individuals susceptible to depression may hold maladaptive schemas, which remain hidden until activated by stressful life events. Dysfunctional beliefs actually reflect the content of these relatively constant schemas (Beck 1972; Beck et al. 1979).

Clinically depressed people have the tendency to experience tremendous feelings of sadness and hopelessness whereas most of the time loose interest in certain activities that they had been enjoy full for them (DSM IV; 2000).

According to a study carried out by Aaron Derfel and Montreal Gazette in 2009, teenagers who consume cannabis regularly or daily can cause damage to their embryonic brains that try to develop at the time. This damage of the brain can make them more susceptible to anxiety later in life and more vulnerable to depression. Research findings on measuring consumption have shown that in Canada there were more teenagers using cannabis than adolescents in Europe. The present study showed findings supporting that when cannabinoid is taken on a daily basis during adolescence then a permanent change in the brain may occur. Due to the publication of these results scientists of the McGill University tried to experiment on teenager and adult rats. The discovery of this experiment was that when rats were exposed for 20 days to cannabis, the teenager rats were negatively affected by the substance. This study was suggesting that the brain of teenagers is still developing until they reach adulthood so for any reason their brain is at a high risk when using cannabis regularly or have been chronic users. Nevertheless, researchers observed two more important aspects of cannabis use, firstly there was a noticeable decrease in serotonin levels in the brain of teenager rats which is a significant neurotransmitter for emotional perception and secondly, researchers noticed an increase in norepinephrine levels which is important for the fight-or-flight response so increased levels of norepinephrine lead to high levels of anxiety. Although cannabis can act as an anti-depressant in medical usage there are findings that may be helpful only for the short-term and has the opposite effects in the long-term (Gabriella Gobbi, 2007).

Childhood trauma is especially associated with a high risk of developing psychosis at a later stage and early onset of substance misuse.

Negative childhood experiences and traumatic situations can actually have significant effect on the health of young teenagers and adults. Post-Traumatic Stress Disorder (PTSD), is a type of anxiety disorder which can arise after you have seen or experienced a disturbing event that involved a threatening or shocking situation which involved the threat of injury and hurt.

Cornelius et al in 2010, carried out a study on the interactions between PTSD among teenagers and the use of cannabis. Researchers reported that PSTD is directly associated with the presence of Cannabis Use Disorder (CUD) and attitude abnormalities. Attitude abnormalities were associated with the existence of Cannabis Use Disorder and PTSD was found to be the mean of association between the two factors. The current findings of the study, suggest that PTSD in fact contributes to the aetiology of CUD among teenagers.

Still, a significant association have been found between PSTD and depression, alcohol, cannabis along with inhalant use whereas the same high association was found between PSTD and cannabis use along with anxiety. Alcoholic young people who were diagnosed at the time were found to be commonly diagnosed with PTSD, also reporting high levels of cannabis and hallucinogen intake (Saban et al; 2010). Concluding PTSD association with cannabis use, cannabinoids gave evidence for an activity of THC on PSTD patients which results in less severe responses acting as a coping mechanism.

In addition to the personality and attitude changes that are based on cannabis use, German Psychiatry of Neurology in 2008 published a study that was carried out in Germany in order to prove the risk of having personality disorders when using cannabis. The German study found that cannabis users between the ages of 17 and 30 years old are more likely to initiate early types of personality disorders compared to non-users of the same age group. Also, differences between sexes were noted, for instance, boys who smoke cannabis were tend to be more antisocial or develop personality disorders whereas girls were tend to be more insecure and depressed. Surprisingly, 90% of the 99 cannabis users developed an anti-social personality disorder later on in their life.

An important aspect that many researchers test until now is the link between cannabis use and violence. Cannabis affects the tendency of heavy users to be violent when experiencing withdrawal symptoms by increasing the levels of cortisol release (Tanda et al, 1997). Cannabis dependence can lead to a violent crime ( Arseneault et al, 2000) whereas a study carried in order to compare the effect of drugs with violence showed a significant link between cannabis ( Friedman et al, 2003). A study of personality differences on monozygotic twins has showed that the cannabis affected twins scored higher in experience seeking and neuroticism than the unaffected twins (Vink JM, Nawijn L, Boomsma DI, Willemsen G. 2007). One of the greatest concerns about smoking cannabis and mental health is that it might be the cause for several illnesses and multiple types of personality disorders.

Yet, a number of up-to-date examination studies supports that cannabis’ use can be very powerful on positive behavioural changes and well-being.

Substance use motives is the final pathway for cannabis use and abuse having variables such as personality factors being less influential ( Cooper; 1994). Motivational factors such as stress factors are associated with alterations in the brain pathways which increase the need for drug seeking however, stress coping interventions and reduce amount of drug intake may help for prevention and recover methods for heavy users (Cox & Klinger; 1990). Cooper in 1994, developed the Drinking Motives Questionnaire Revised ( DMQ-R) in order to measure the four drinking motives which were enhancement , coping , social and conformity. The internal motives which are enhancement and coping were found to be highly associated with the fire up of drinking (Kuntsche et al; 2005). The four motives were found to be highly associated with drug use thus Simon and colleagues in 1998 adapted the measure by shifting from alcohol to cannabis. After the changes took place on the measure, they added a subscale on the enhancement of perceptual and cognitive experiences from cannabis supporting that these motives had an association with regular use of cannabis and subsequent consequences (Simons, Carey, Borsari; 1998). The cannabis’ model found great associations in use related problems suggesting that cannabis motivational factors may be stronger predictors than alcohol motivational factors in use related problems (Simons et al; 1998). Individuals who use cannabis in order to change internal conditions such as coping and enhancement may use cannabis more heavily or chronically than others (Cooper; 1994, Tate et al; 1994). However, individuals who use cannabis for negative support reasons for instance coping and conformity usually result in problematic behaviours (Cooper;1994, Simons et al; 1998).


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The Effects of Cannabis on Health and Personality. A Study
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