Longitudinal changes in endocannabinoids and clinical course of adolescent non-suicidal self-injury.

Non-suicidal self-injury (NSSI) in adolescents has previously been linked to alterations in the endocannabinoid system. While increasing evidence supports endocannabinoid levels as potential biomarker in psychiatric care, little is known about their longitudinal trajectories over the course of treatment or in predicting clinical symptoms. This is the first study to investigate endocannabinoids in a longitudinal cohort of patients with NSSI, exploring associations with the development of symptoms over time. Plasma endocannabinoids and NSSI, using the German version of the Self-Injurious Thoughts and Behaviors Interview (SITBI-G), were assessed in n = 47 female adolescents with NSSI at both baseline and after one year of treatment (follow-up). Associations between endocannabinoid levels and clinical symptoms over time were analyzed. Anandamide (AEA) significantly decreased from baseline to follow-up while 2-arachidonoylglycerol (2-AG) increased after one year. While lower AEA levels have previously been reported in adolescents with NSSI, this longitudinal study found that AEA decreased over one year despite an overall improvement in NSSI symptoms. The overall pattern suggests that changes in circulating endocannabinoids do not closely correspond to symptom improvement. These findings indicate that circulating endocannabinoid levels change over time in adolescents with NSSI, but their complex and partly inconsistent associations with clinical symptoms limit their clinical utility as biomarkers.