Depressive symptoms and anhedonia
The number of depressive symptoms present at time of interview were scored based on the youth diagnostic interview K-SADS. Positive symptoms were recorded as present based on affirmative answers to the following: hypersomina, fatigue, concentration disturbance, indecision, decreased appetite, weight loss, increased appetite, weight gain, psychomotor agitation in depressive disorder, psychomotor retardation, guilt, hopelessness, decreased self-esteem, impairment in functioning due to depression, depressed mood, irritability and anhedonia. 146 subjects had at least one or more depressive symptoms. Of these, the mean number of depressive symptoms was 3 (sd 2, median 3, range 1 - 11). Depressive symptom scores were not available for 27 subjects. Depressive symptoms were also binarised (present vs. not present) for additional regression analysis. 75 subjects reported anhedonia.
Behavioural task in fMRI scanner: Monetary Incentive Delay task
The fMRI Monetary Incentive Delay (MID) task measures domains of reward processing, including anticipation of reward, our interest here. Each trial of the MID task begins with an incentive cue of five possible trial types (Win $.20, Win $5, Lose $0.2, Lose $5, $0 - no money at stake), a delay, a target during which the participant responds to either win money of avoid loosing money and feedback. Each participant receives 40 reward and loss anticipation trials and 20 no money anticipation trials.
The task was programmed in E-Prime professional 2.0 versions 2.0.10.356 or later. The tasks and stimuli are available for download at http::
fablab.yale.edu/page/assays-tools. The response collection device was harmonised for precision in response latency across all tasks and all sites with a Current Designs 2-button box. The task was programmed to accept input from the dominant hand. No mandate for precise visual or auditory resolution was imposed across sites.
Task performance was individualised with the initial response target duration based on the participants performance during a practice session prior to scanning. Performance was calculated as the average reaction time (RT) on correct trials plus two standard deviations. To reach a 60% accuracy rate, the task difficulty was adjusted over the course of the task after every third incentivised trial based on the overall accuracy rate of the previous six trials. For feedback, the adaptive algorithm results in 24 positive feedback trials (for both reward and loss) and 16 negative feedback trials (for both reward and loss) on average. Subjects were excluded if participant did not have an acceptable performance in task (this was assessed based on the threshold that all trial types must yield more than 3 events for both positive and negative feedback (n =127)) (indicated in database by mid$beh_mid_perform_flag).
Imaging Protocols