Cannabis is the most commonly used drug in the UK after alcohol and tobacco, however only 1 in 8 adults and 1 in 5 young people have admitted to using it in the last year (FRANK, 2013). The main active ingredients in cannabis are delta-9-tetrahydrocannabinol (THC) and this is what causes the ‘high’ and cannabidiol (CBD) which acts as a counterbalance, making you feel alert and creative (Alexandrou, 2011). THC is the main ingredient which has been linked to causing long-term neuropsychological damage. During the past 10 years, stronger strains of cannabis have become more popular, with an increase from 6% to 16 % THC with less CBD (Alexandrou, 2011). This is thought to have caused an increase in cannabis related neuropsychological harm. Much of the leading research into the long-term effects of marijuana, suggests that regular, long-term use of marijuana leads to deficits in IQ, executive functioning, motor and learning skills and short-term memory loss(Grant, Gonzalez, Carey, Natarajan, & Wolfson, 2003; Pope, Gruber,& Yurgelun-Todd, 1995; Pope, Gruber, Hudson, Huestis, & Yurgelun-Todd, 2001; Solowij & Battisti, 2008; Grant et al., 2003; as cited by Nehal P. Vadhan, Wilfred G. van Gorp, and Frances R. Levin 2011; Solowij, 2002; Harvey, Sellman, Porter & Frampton, 2007). However, there are debates among the critics as to how ‘long-term’ these effects are, who they are most likely to affect and the cause of the neuropsychological damage.
One particularly influential study concerning the use of marijuana and long-term neuropsychological damage suggests that abstaining from smoking marijuana for more than 28 days may reverse the neuropsychological damage it causes (Pope et al., 2001). However, some critics have found differences in the motor and learning skills of long-term users even after two years of abstaining when compared to those who have never
References: Alexandrou, J. (2011). Cannabis: what’s the harm [video file]. Retrieved 27/2/2013 from http://www.youtube.com/watch?v=RifN6EOajKU FRANK (2013) Talk to frank: cannabis: find out the facts Gruber SA, Sagar KA, Dahlgren MK, Racine M, Lukas SE (2011) Age of onset of marijuana use and executive function. Psychol Addict Behav, 10.1037/a0026269. Harvey MA, Sellman JD, Porter RJ, Frampton CM (2007) The relationship between non-acute adolescent cannabis use and cognition Lundqvist, T. (2005). Cognitive consequences of cannabis use: Comparison with abuse of stimulants and heroin with regard to attention memory and executive functions. Pharmacol. Bioche. Behav., 81 (2) pp. 319-330. Meier, M Papathanasopoulos, P., Messinis,L., Lyros, E., Kastellakis, A. & Panagis, G. (2008). Multiple Sclerosis, Cannabinoids, and Cognition. The Journal of Neuropsychiatry and Clinical Neurosciences, 20. Pp 36-51. Pope, H. G., Jr., Gruber, A. J., Hudson, J. I., Huestis, M. A., & Yurgelun-Todd, D. (2001). Neuropsychological performance in long-term cannabis users. Archives of General Psychiatry, 58(10), 909-915. Solowij N, Stephens RS, Roffman RA, et al. Cognitive Functioning of Long-term Heavy Cannabis Users Seeking Treatment. JAMA. 2002;287(9):1123-1131. doi:10.1001/jama.287.9.1123.