In an open-label retrospective analysis of 35 Veterans with co-occurring depression and PTSD, repeated intranasal (S)-ketamine treatments over four weeks were associated with reductions in both depression and PTSD symptoms. Depression scores on the PHQ-9 fell by an average of 5.1 points, from 19.8 to 14.7, with 14% of patients showing a clinically meaningful response. PTSD scores on the PCL-5 dropped by an average of 15.5 points, from 54.8 to 39.3, with 46% showing a clinically meaningful response. Changes in depression and PTSD symptoms were only moderately correlated, and some individuals experienced PTSD improvement without antidepressant response, suggesting distinct mechanisms of action for the two conditions.
Posttraumatic stress disorder (PTSD) is linked to poor hippocampal function and disrupted pattern recognition. Cannabis use is common among people with PTSD, but its impact on these cognitive functions is unclear. In 111 participants with varying PTSD symptoms, regular and minimal cannabis users completed a mnemonic similarity task. High PTSD symptoms were associated with reduced pattern separation in minimal users. Regular users with high PTSD symptoms showed greater pattern separation, while those with low PTSD symptoms showed reduced pattern separation. The results suggest regular cannabis use may disrupt pattern separation and hippocampal-dependent processes, but may improve it in individuals with high PTSD symptoms. The cross-sectional design requires longitudinal follow-up to evaluate causal effects.