Paradoxical Decrease in Striatal Activation on an fMRI Reward Task Following Treatment in Youth with Co-morbid...

Area of Science:

• Neuroscience
• Psychiatry
• Addiction Medicine

Background:

• Reward behavior is mediated by the brain's reward system, including the ventral striatum.
• Comorbid conditions like cannabis dependence and major depression present unique challenges in treatment and neurobiological study.

Purpose of the Study:

• To examine changes in reward-related brain activity using fMRI before and after a 12-week treatment for adolescents with co-occurring cannabis dependence and major depression.
• To test the hypothesis that treatment would increase reward system activation as depressive symptoms and cannabis use decline.

Main Methods:

• Utilized fMRI to assess brain activity during a reward task in six adolescents before and after a 12-week treatment period.
• Participants received Cognitive Behavioral Therapy/Motivational Enhancement Therapy (CBT/MET) and were randomized to fluoxetine or placebo.

Main Results:

• fMRI confirmed activation in reward-related areas (insula, prefrontal, striatal) both pre- and post-treatment.
• Contrary to hypotheses, participants exhibited lower reward-related activation post-treatment compared to pre-treatment.
• This paradoxical finding suggests the impact of treating cannabis use disorder may diminish the expected increase in reward activity from depression treatment.

Conclusions:

• Treatment for comorbid cannabis dependence and major depression in adolescents led to a decrease in reward-related neural activation.
• The findings highlight the complex interplay of comorbid disorders and their influence on brain activity during treatment.
• Emphasizes the critical need to consider comorbid conditions in neuroimaging studies of psychiatric and substance use disorders.