Endocannabinoid levels in female-sexed individuals with diagnosed depression: a systematic review

Abstract

BackgroundMajor depressive disorder (MDD) is a highly prevalent mental health disorder with females experiencing higher rates of depression (11.6%), anxiety (15.7%) and physiological distress (14.5%) than males. Recently, the Endocannabinoid system (ECS) has been proposed to be a key contributing factor in the pathogenesis and symptom severity of MDD due to its role in neurotransmitter production, inflammatory response and even regulation of the female reproductive cycle. This review critically evaluates evidence regarding ECS levels in female-sexed individuals with depressive disorders to further understand ECS role.Materials and methodsA systematic literature review of available research published prior to April 2022 was identified using PubMed (U.S. National Library of Medicine), CINAHL (EBSCO), Web of Science, AMED and Scopus (Elsevier). Studies were included if they reported ECS analysis of female-sexed individuals with depression and were excluded if they did not differentiate results between sexes, assessed mental health conditions other than depression, tested efficacy of endocannabinoid/n-acylethanolamine/cannabis or marijuana administration and that were unable to be translated. Critical appraisal of each included study was undertaken using the Joanna Briggs Institute Critical Appraisal Tool for Systematic Reviews.ResultsThe 894 located citations were screened for duplicates (n = 357) and eligibility by title and abstract (n = 501). The full text of 33 studies were reviewed, and 7 studies were determined eligible for inclusion. These studies indicated that depressed female-sexed individuals have altered levels of ECS however no significant pattern was identified due to variability of study outcomes and measures, limiting overall interpretation.DiscussionThis review suggests potential involvement of ECS in underlying mechanisms of MDD in female sexed-individuals, however no pattern was able to be determined. A major contributor to the inability to attain reliable and valid understanding of the ECS levels in female-sexed individuals with depression was the inconsistency of depression screening tools, inclusion criteria’s and analysis methods used to measure eCBs. Future studies need to implement more standardised methodology to gain a deeper understanding of ECS in female-sexed individuals with depressive disorders.Trial registration This review was submitted to PROSPERO for approval in April 2022 (Registration #CRD42022324212).