This paper explores the long term effect of cannabis on mental health by examining the research on follow-up studies, case studies, online surveys, and clinical trials. Cannabis contains Delta-9-tetrahydrocannabinol (∆9-THC), which is the psychoactive cannabinoid that is hypothesized to be responsible for the development of schizophrenia and depression. Cannabis also contains Cannabidiol (CBN), the cannabinoid with antipsychotic properties that has been hypothesized to counter-balance the psychotic properties of Delta-9-tetrahydrocannabinol (∆9-THC) and to be used as a treatment for people suffering from schizophrenia. Many people diagnosed with schizophrenia, and many people diagnosed with depression, use cannabis. Both mental disorders have been correlated with cannabis use. Scientists today still argue about whether cannabis alone is the cause of these disorders. Many studies demonstrate a clear correlation between cannabis use and mental health disorders. However, none of the studies can conclude that cannabis is the sole cause of the development of the disorders.
Keywords: Delta-9-tetrahydrocannabinol (∆9-THC), Cannabidiol (CBN), cannabinoid, schizophrenia, depression
Author Note: Cannabis is illegal in many countries, for this reason experimental science regarding cannabis is also illegal unless granted by the government. Because there are such strict regulations on experimental science regarding cannabis appropriate, research-grade samples are tough to attain.
Cannabis and Mental Health:
The Effect of Cannabis on Schizophrenia and Depression
Cannabis has been associated with schizophrenia and depression for a very long time. There are numerous studies that show correlation between cannabis and schizophrenia and depression. There are also studies that contradict this long time association and illustrate an inverse correlation between cannabis and schizophrenia and depression (Denson & Earlywine 2006). This paper reveals the common problems with mistaking correlation and causation. As stated in an interview with Pers Hambric (2011) “Just because two events occur at the same time does not imply that they share a cause and effect relationship”.
Cannabis use is frequent among schizophrenic patients. Delta-9-tetrahydrocannabinol (∆9-THC) is the psychoactive compound of cannabis that allegedly causes the development of schizophrenia (Zammit S, Allebeck P, Andreasson S, Lundberg I, and Lewis G, 2002). Researchers are still unsure whether or not this psychoactive compound is the sole cause of the development of schizophrenia or a form of a schizophreniform disorder. There is research that suggests a person that is genetically pre-determined to develop schizophrenia or form of a schizophreniform disorder may be more inclined to use cannabis (Arseneault et al. 2002).
In 1987, Zammit et al. (2002) studied the association of cannabis use and the development of schizophrenia during a 15 year follow up of 45, 570 Swedish conscripts. At the time, these 45, 570 Swedish conscripts accounted for 97% of the population (Zammit et al., 2002). The study showed a definite correlation between cannabis and schizophrenia. Those who told their doctors that they had used cannabis more than 50 times before the age of 18 turned out to be six times as likely to develop schizophrenia in the next 15 years as those who used cannabis less than 50 times (Zammit et al., 2002). The study shows a dose dependent relationship between cannabis use and schizophrenia. This study fails to prove causation because of many uncontrolled factors. First, Zammit et al. could not control for the use of other drugs. Second, symptoms that preceded cannabis use were neither documented nor considered in the results. The men that developed schizophrenia later in life may have done so whether or not they decided to use cannabis. Lastly, the study completely relied on the conscripts to honestly self-report their cannabis use.