Does Terpene Use Affect Memory Consolidation?
How does cannabis affect memory? Many know from either personal or anecdotal experience that cannabis use can cause short-term memory dysfunction and loss. Research has determined that this effect increases in magnitude in correlation with increased use; chronic smokers have more pronounced and even irreversible changes to their memory consolidation.  These results were confirmed with a functional magnetic resonance image, or MRI, which unlike a regular MRI that takes static images, instead takes a real-time recording of what goes on in the brain and body. 
A meta-analysis of the current literature compared the memory modulation of cannabis in both healthy users and those with what they termed as “psychotic disorders”.  What is very interesting is that they found that lower levels of depression seem to be associated with a lesser degree of memory impairment. Also of note, in the “psychosis” group, cannabis-users had lower levels of depression, whereas in the control group, cannabis-users had higher depression scores than age-matched non-users. This implies that people with co-morbidities (simultaneous presence of two chronic conditions) are less likely to experience memory impairment from cannabis use than healthy individuals.
Even though we may intuitively think of this as being true, it was recently scientifically shown that prolonged and continued abstinence from cannabis use reverses memory deficits which were previously found in chronic cannabis users, particularly in the demographic of young adults.  Relatedly, people with mental illnesses such as schizophrenia tend to use cannabis as a way to manage their condition symptomatically, and this exposure may exacerbate certain facets of their disease. Encouraging abstinence from cannabis in this demographic can have an effect more pronounced than that seen in the general population.  Developing interventions for cannabis use disorder in patients with schizophrenia that focus on appropriate identification and therapy is therefore an important clinical goal moving forward.
Interestingly, the memory-impairing side-effect of cannabis is currently hypothesized to be responsible for the mechanism of action underlying the therapeutic role cannabinoids may play in the treatment of post-traumatic stress disorder, or PTSD.  Without going into too much detail, pharmacological treatment for PTSD today relies on “memory disruption”, which involves stopping the traumatic memory as it replays in a person’s head, literally giving the brain a chance to rewire those damaged neural pathways.
This shows that whether or not an effect of a drug is considered good or bad really depends on the situation. For example, opioids tend to make people constipated, which is often viewed as a negative side effect. But, when formulated differently, the non-analgesic opioid agent loperamide (brand name Imodium™) makes an excellent anti-diarrheal. Such seems to be the case with cannabis and memory.
There is still a lot that we don’t know, however. No study has assessed whether memory problems extend to a concept called episodic foresight, “a core component of which is the ability to mentally travel into one’s personal future”.  Furthermore, no study has yet looked at the combinatorial effect of how stress impacts the memory consolidation in cannabis users.  This preliminary clinical study revealed detrimental effects of acute stress on prospective memory performance, which may be exacerbated in cannabis users who often consume cannabis in an effort to deal with ongoing stress.
So, while cannabis science has come very far, there is still a lot further it needs to go.
- Lisdahl, K.M. et al. “Considering Cannabis: The Effects of Regular Cannabis Use on Neurocognition in Adolescents and Young Adults”. Curr Addict Rep. 2014; 1(2): 144–156 [Times cited = 90, Journal impact factor = 3.880].
- Jager, G. et al. “Long-term effects of frequent cannabis use on working memory and attention: an fMRI study”. 2006; 185: 358–368 [Times cited = 171, Journal impact factor = 3.222].
- Schoeler, T. et al. “The effects of cannabis on memory function in users with and without a psychotic disorder: findings from a combined meta-analysis”. Psychol Med. 2016; 46(1): 177-88 [Times cited = 37, Journal impact factor = 6.159].
- Schuster, R. et al. “T266. Memory Deficits are Reversible With Sustained Cannabis Abstinence Among Cannabis Using Adolescents”. Biological Psychiatry. 2018; 83(9): S233 [Times cited = 0, Journal impact factor = 11.412].
- Rabin, R.A. et al. “Effects of Extended Cannabis Abstinence on Cognitive Outcomes in Cannabis Dependent Patients with Schizophrenia vs Non-Psychiatric Controls”. Neuropsychopharmacology. 2017; 42(11): 2259–2271 [Times cited = 7, Journal impact factor = 6.399].
- Stern, C.A. et al. “On Disruption of Fear Memory by Reconsolidation Blockade: Evidence from Cannabidiol Treatment”. Neuropsychopharmacology. 2012; 37: 2132–42 [Times cited = 86, Journal impact factor = 6.399].
- Mercuri, K. et al. “Episodic foresight deficits in regular, but not recreational, cannabis users”. J Psychopharmacol. 2018; 32(8): 876-882 [Times cited = 3, Journal impact factor = 4.738].
- Cuttler, C. et al. “Joint effects of stress and chronic cannabis use on prospective memory”. Psychopharmacology. 2019; doi.org/10.1007/s00213-019-5184-9 [Times cited = 0, Journal impact factor = 3.222].
Image Credit: Spandan