Health and Psychological Effects of the Use of Marijuana. Research review

Marijuana and Psychotic disorders like Schizophrenia

Psychotic disorders typically include odd thoughts, auditory hallucinations and inappropriate emotions (Earlywine, 2002). Many studies have suggested the involvement of marijuana abuses leading to certain symptoms or aspects of psychosis like schizophrenia (Mass et al., 2001). The comparative study done by Fridberg et al., (2011) has shown higher measures of schizotypal personality traits among chronic marijuana users than non-users. However, this research could not assess the initial psycho-analysis of cannabis users before they start using it. Also, this study has not included the post drug use state of the subjects which is the key factor in determining the effect of cannabis as many studies have suggested that the psychosis symptoms caused by the use of marijuana dissipate relatively quicker whereas schizophrenia remains as chronic mental illness. The relation of marijuana use to the development of psychosis is unclear as the studies on marijuana abuse have not shown the elevated neuroticism relative to controls as it has been seen in the studies done among chronic users of other substances (Walton & Roberts, 2004).

The fact that the prevalence of schizophrenia has not been increased along with the increase in the rate of the use of marijuana, the studies suggesting marijuana causing schizophrenia requires more investigations. In fact, schizophrenia is no more prevalent during historical periods of extensive marijuana consumption than any other time (Hall & Solowij, 1998, as cited in Earlywine, 2002). In support of these arguments Cohen et al., (2011), categorically defined schizophrenic individuals and control groups and investigated the effect of marijuana which demonstrates the strong evidence of a link between schizotypy and both greater use of marijuana and its related problems in schizophrenia than in control groups.

Morrison et al., (2009), carried out the study of effects of marijuana from a neurobiological perspective in healthy participants only and found that the use of marijuana enhanced the transient symptoms of odd thoughts, auditory hallucinations, emotions and motivation systems. Therefore, relating the findings of these studies suggest the idea that the individuals with negative schizotypy who may already have experienced psychotic dysfunctions to some degree may exacerbate the symptoms with the use of marijuana. So, recent studies have shown clear evidence against the marijuana as the causative factor for psychotic disorders however, marijuana may exacerbate psychotic symptoms in schizophrenics. Moreover, psychotics who use marijuana regularly have more hospitalizations with worse symptoms (Caspari,1999).

Marijuana and cognitive disorders

Although recent studies (Calderia et al., 2008, Cohen et al., 2011, Morrison et al., 2009) have ruled out the effect of marijuana to cause chronic mental illness like schizophrenia, psychosis, and anxiety, they have reported strong evidence supporting the effect of marijuana in the acute cognitive functions in human. Many experiments in recent decades have proved that marijuana use impairs memory, attention, inhibitory control, executive functions, reaction time and decision making (Solowij et al., 2010). However, the extent to which such cognitive deficits persists after acute intoxication or long term regular use is a controversial area for debate. Curran et al. (2002) have reported the cognitive dysfunction in marijuana users during and for several hours after smoking. Pope, HG., (2001) have reported cognitive dysfunction for few days following intoxication whereas Bolla, KI., (2002) have demonstrated lasting cognitive impairments following cessation of marijuana use for more than a month. These studies only describe the duration of effects of marijuana in cognitive dysfunctions but could not describe various parameters of marijuana use which can cause these effects.

Novaes et al. (2005), examined sustained attention tasks in 132 long term users who were grouped into early onset group (<15 years of age) and a late onset group (≥15 years of age). Early-onset users were found to perform weaker than the late onset group and more interestingly there was no significant performance difference between the late onset group and controls. However, this study could not determine the effects of dose, frequency, and quality of marijuana that the subjects have been using which may have great influence in the results.

Raumaekers et al. (2009), included a higher dose of 500µg/kg Tetrahydrocannabinol (THC) in their study, which found that only occasional users showed impaired performance in a divided attention task whereas both occasional and heavy users exhibited inhibitory control deficits in a Stop Signal task. This study included a different category of subjects, dose, and type of task which has increased its reliability. However, this research possesses lesser validity as 500µg/kg THC use as the higher dose for the different age group is a hypothetical measurement. Moreover, since no studies have given specific dose as the high and low dose for different age groups of people further studies is needed to determine the effects of a particular dose of marijuana to the particular group of subjects, types of tasks and cognitive behaviors.

Marijuana and memory impairment…..