Depressive symptoms in adolescents: associations with white matter volume and marijuana use.
BACKGROUND
Depressed mood has been associated with decreased white matter and reduced hippocampal volumes. However, the relationship between brain structure and mood may be unique among adolescents who use marijuana heavily. The goal of this study was to examine the relationship between white matter and hippocampal volumes and depressive symptoms among adolescent marijuana users and controls.


METHODS
Data were collected from marijuana users (n = 16) and demographically similar controls (n = 16) aged 16-18. Extensive exclusionary criteria included psychiatric and neurologic disorders, including major depression. Substance use, mood, and anatomical measures were collected after 28 days of monitored abstinence.


RESULTS
Marijuana (MJ) users demonstrated more depressive symptoms than controls (p < .05). MJ use (beta = .42, p < .005) and smaller white matter volume (beta = -.34, p < .03) each predicted higher levels of depressive symptoms on the Hamilton Depression Rating Scale. MJ use interacted with white matter volume (beta = -.55, p < .03) in predicting depression scores on the Beck Depression Inventory: among MJ users, but not controls, white matter volume was negatively associated with depressive symptoms.


CONCLUSIONS
Marijuana use and white matter volume were additive and interactive in predicting depressive symptoms among adolescents. Subtle neurodevelopmental white matter abnormalities may disrupt the connections between areas involved in mood regulation.
Medina
Krista Lisdahl
KL
Department of Psychiatry, University of California, San Diego, USA.
Nagel
Bonnie J
BJ
Park
Ann
A
McQueeny
Tim
T
Tapert
Susan F
SF
D000293:Adolescent; D002186:Cannabinoids / Q000009:adverse effects; D002540:Cerebral Cortex / Q000187:drug effects / Q000473:pathology*; D015897:Comorbidity; D003866:Depressive Disorder / Q000139:chemically induced / Q000175:diagnosis* / Q000453:epidemiology; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D020712:Fornix, Brain / Q000187:drug effects / Q000473:pathology; D006624:Hippocampus / Q000187:drug effects / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008326:Mammillary Bodies / Q000187:drug effects / Q000473:pathology; D008385:Marijuana Smoking / Q000009:adverse effects* / Q000453:epidemiology; D015999:Multivariate Analysis; D020534:Parahippocampal Gyrus / Q000187:drug effects / Q000473:pathology; D010552:Personality Assessment; D012016:Reference Values; D012307:Risk Factors
D002186:Cannabinoids