Study shows cannabis use decreases symptom severity after a concussion

This article originally appeared in the 1/23/20 Concussion Update Newsletter: "Why recovery is highly personal.” This is a modified version of the article. 

In an interview with The Varsity, Dr. David Lawrence discusses a study he co-authored regarding how cannabis, alcohol, and cigarettes affect concussion symptoms and recovery. The study, published in Brain Injury, followed 307 subjects for four weeks after their concussion to track their recovery. 

Lawrence et al.’s analysis of the recovery process showed that recovery to cognitive and physical activities in the acute period following concussion were not affected by cannabis, alcohol, and cigarette use.

The authors further analyzed individuals who were still recovering from their concussion after a period of four weeks. They observed that for these individuals, cigarette use was associated with a higher symptom severity score in the first week of recovery. However, in subsequent weeks, cigarette use did not impact symptom severity. 

Furthermore, they found that cannabis use was associated with lower symptom severity in the third and fourth week. Finally, alcohol use was not associated with symptom severity scores at any of the four weekly assessments.

Therefore, among unrecovered individuals, post-concussion cannabis use was associated with lower symptom severity, and post-concussion cigarette use was associated with higher initial symptom severity.

However, this study had several limitations. For instance, data collected on patients’ cannabis, alcohol, and cigarette use were self-reported. In addition, the categorization of moderate and heavier drinkers in the same group may have altered results. Moreover, because participants were tracked for only four weeks, the recovery process beyond this time period could not be examined.

Dr. Lawrence himself suggests all individuals follow current clinical recommendations on the use of cannabis, alcohol, and cigarettes, which is to avoid these substances. He says that “we would still recommend to [stop] use until further research supports or negates their use.”