Results from a systematic review published in Journal of Clinical Psychiatry revealed a link between recent cannabis use and negative long-term symptoms and treatment outcomes among people with anxiety and mood disorders.
“Many individuals who live with an anxiety or mood disorder claim to use cannabis to relieve acute symptoms. However, whether cannabis benefits or harms symptoms over time is still a matter of debate,” George Mammen, PhD, from the Institute for Mental Health Policy Research, Centre for Addiction and Mental Health in Toronto, told Healio Psychiatry. “It is important to conduct more research to help understand the associations between cannabis use and long-term symptomatic/treatment outcomes, which clinicians can then use to inform their own, and their patients’, knowledge of cannabis’ potential effects.”
Mammen and colleagues conducted a systematic review of prospective studies to examine the longitudinal connections between cannabis use and symptomatic outcomes in patients with anxiety or mood disorders. The investigators searched clinical databases for relevant literature that included (1) adults with mood or anxiety disorder at baseline, (2) an independent variable focusing on cannabis use and (3) a dependent variable focusing on the symptoms and/or outcomes in anxiety and mood disorders.
In total, 12 studies encompassing 11,959 individuals — four of which related to PTSD, one to panic disorder, five to bipolar disorder and two to depressive disorder — were included in this review. Of these, 11 studies showed that recent cannabis use, defined as any and/or greater frequency of use during the previous 6 months, was tied to higher symptomatic levels of anxiety and mood disorders over time compared with no and/or using cannabis less frequently.
“There is no indication that cannabis use (use within the last 6 months) may benefit symptoms of an anxiety or mood disorder over time (ie, up to 5 years later),” Mammen said. “Rather, there is indication that – among individuals living specifically with PTSD, panic disorder, bipolar disorder or a depressive disorder – using cannabis is associated with negative symptomatic outcomes over time. Compared to those who did not use cannabis, those who used cannabis were more likely to experience long-term persistent symptoms and higher severity of symptoms.”
Furthermore, 10 of these studies indicated that cannabis use was linked to less symptomatic improvement from treatment with medication and/or psychotherapy for anxiety and mood disorders.
“Additional research is still needed to better understand the association between cannabis use and anxiety or mood disorders,” Mammen told Healio Psychiatry. “Despite the evidence provided in our study showing an association between cannabis use and negative long-term symptoms, the current findings should be interpreted with caution when considering the way the study was carried out (not a clinical trial), the individuals involved (inpatients with higher severity of symptoms), and the illegal source of cannabis consumed (with typically more potent levels of [tetrahydrocannabinol], which is the psychoactive compound that causes the 'high').” – by Savannah Demko
Disclosure: The authors report no relevant financial disclosures.
Editor's note: This story was updated on July 20 to add comments from the study author.