Self-medication hypothesis

On the other hand, the self-medication hypothesis predicts that individuals may be using cannabis due in large part to their predisposition for psychosis - so in other words it is the psychosis which is influencing young people to use the drug rather than the case of the reverse.

A study conducted by Hamera et al. (1995) examined correlations over 84 consecutive days between self reported psychotic symptoms, licit and illicit drug use and medication compliance in 17 individuals with schizophrenia. They only found relationships between nicotine and prodromal psychotic symptoms and between caffeine use and symptoms of anxiety and depression but no relationships were found between psychotic symptoms and alcohol or cannabis use. Measurement in this study was self-monitored though and so this, along with the fact that there were relatively low rates of heavy drug use in a small sample, may be one of the major limiting factors of this study. Another study concluded that cannabis use did not precipitate the development of psychosis even when the individuals were considered at-risk for developing it (Phillips et al 2002). A more comprehensive 14-year follow-up study of 1580 Dutch individuals showed that cannabis use predicted future psychotic symptoms even when subjects were free of psychotic symptoms at baseline (Ferdinand et al 2005) which goes against the cannabis as causation hypothesis. The authors note however that those subjects who did have the presence of psychotic symptoms before cannabis use were also at risk for cannabis use at follow up and so unlike the study before, the directional relationship between cannabis and psychosis is unclear here and may support the self-medication hypothesis.

Many studies have pointed to the drug's euphoric effects which may help to relieve the various "negative symptoms" (loss of or decreased motivation, loss of or decreased in ability to take initiate or come up with new ideas, loss of or decreased talking, difficulties expressing emotion, difficulties thinking and/concentrating) as well as depression.

While there are numerous quantitative studies on the link between psychosis and cannabis and there have been a few studies looking at the reasons why people with mental illness smoke cannabis (Boys, Marsden & Strang, 2001; Gregg, Barrowclough & Haddock, 2009; Healy et al. 2009), there is still a paucity of qualitative literature examining this link. In one early study, Dixon et al. surveyed 83 patients with schizophrenia and results showed that cannabis reduced anxiety and depression, and increased a sense of calm, though sometimes at the cost of increased suspiciousness (1990). Very recently however, Lobbana et al. set out to understand the factors influencing substance use in people with psychosis from a qualitative perspective (2010). The authors discovered four main themes in the participant interviews that seemed to be the important factors influencing the young peoples' cannabis use.

First of all, many young people viewed drug use (especially cannabis) as a "normal" and widely accepted part of their local realities and activities. Some participants mentioned that cannabis helped to improve their social behavior. There was also a positive connotation attached to cannabis culture for even those participants who didn't express this view. These participants didn't see drug taking as being part of the "normal" culture but rather prided themselves as being part of a subversive movement wherein using cannabis was about subverting perceived social norms.  So in both cases there was not a lot of stigma attached to cannabis use and even if stigma was perceived, in these cases participants saw this as part of its subversive or "edgy" appeals. Accordingly, the influence of perceived drug norms was conceptualized by the authors as being a significant factor leading towards experimentation and use of cannabis for young people with psychosis.

Secondly, participants made both external and internal attributions for their use. For those who made an internal attribution (i.e. using was an active personal choice) there was a tendency to emphasize the positive effects of the cannabis use on their social lives. Smoking cannabis was seen as a way to connect and relate to others. On the whole it was seen (at least at first) as a fun and enjoyable experience and a mechanism to improve their interpersonal relationships. For those who made external attributions for their use (i.e. use was due to the influence of others) there was a tendency to give the impression that cannabis use had been inevitable and they positioned themselves in a passive role in terms of how they came to use cannabis. These participants describe that memberships in their peer groups are strengthened and grow around drug use and that there is pressure to keep using because the young people fear an overt or covert form of social isolation from their peers if they stop using. So, in both cases the motivation to use is triggered by social pressures which is not unlike typical reasons why any young person, psychotic or not, may use cannabis.

Next, the authors noted that this desire to belong and be accepted can function to both initially instigate and continue drug use but also to terminate it. For the participants who had reduced or stopped using cannabis there had been a change in their personal life goals, particularly in terms of an increase in the perceived value of health, disposable income and close family relationships. The social function of cannabis use still featured prominently but in this case it was in the context of participants explaining how they knew they had a problem and needed to stop. The social aspect of cannabis use was a big component for participants- so much so that if it started to be used by the young people in isolation, it was seen as an anomaly and a sign of a problem. The older participants were the ones who tended to talk about their decreased drug use and the accompanying change in life goals. This fits with general trend for there to be a natural decrease in drug use no matter what the population.

Finally, participants' beliefs about the links between mental health and drug use were seen as playing a role in their drug using behavior. Some participants had an intuitive sense of the biosocial model or stress diathesis model in their explanations of cannabis use. They put out the idea that they already had a predisposition for mental illness (e.g. history mental illness in the family) and that the drug may have shaped the outcome or pathway for their psychosis trajectory.  Other participants explained that cannabis or drugs in general were a coping mechanism for their mental health problems. These young people used some of the effects of the drugs to self-medicate the symptoms of their own mental illness. For example, one young man described having insomnia and the cannabis helping him get to sleep. Another young person described the cannabis as a way to temporarily relieve depression and anxiety. One participant even described how using cannabis helped him to cope with his psychotic voices. He explained that he felt like drug use was a better and less anxiety provoking explanation for hearing voices. On the other hand several participants noted that using cannabis for symptom management was too unpredictable in the long run and could actually exacerbate their symptoms. 

The young people repeatedly highlighted the ability that the cannabis has to help alleviate negative mood and boost social connectivity and the authors note that this is particularly pertinent to this population because early psychosis tends to affect people during adolescence and young adulthood. This is a stage where the need to fit in with ones' peers and to experiment are important developmental markers. This combined with the fact that a lot of people suffering from psychosis experience negative symptoms (which are likely to make them feel a lot more socially isolated than their peers) may explain why many young people are motivated to try and then continue to use cannabis. 

Ultimately, this claim that young people may be self-medicating by using cannabis seems somewhat understandable given the rich responses given by the participants in this particular study. However, more work, specifically more qualitative work, should be done in order to gain further insight into the reasons and motivations that young people with psychosis are using cannabis.   The implications of this are vast in terms of developing awareness campaigns, interventions and strategies that get at the root of these motivators. The likelihood of developing programs and materials that are actually useful is much higher if the young peoples' perspectives have been carefully considered.

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