Objective: Major depressive disorder (MDD) has been associated with executive dysfunction and related abnormal prefrontal activity, whereas the status of executive function (EF) in frequently co-occurring anxiety disorders and in comorbid depression-anxiety is unclear. We aimed to study functional MRI correlates of (visuospatial) planning in MDD and anxiety disorders and to test for the effects of their comorbidity.
Method: Functional MRI was employed during performance of a parametric Tower of London task in out-patients with MDD (n = 65), MDD with comorbid anxiety (n = 82) or anxiety disorders without MDD (n = 64), and controls (n = 63).
Results: Moderately/severely depressed patients with MDD showed increased left dorsolateral prefrontal activity as a function of task load, together with subtle slowing during task execution. In mildly depressed and remitted MDD patients, in anxiety patients, and in patients with comorbid depression-anxiety, task performance was normal and no activation differences were observed. Medication use and regional brain volume were not associated with altered visuospatial planning.
Conclusion: Prefrontal hyperactivation during high planning demands is not a trait characteristic, but a state characteristic of MDD without comorbid anxiety, occurring independent of SSRI use. Disturbances in planning or the related activation are probably not a feature of anxiety disorders with or without comorbid MDD, supporting the current distinction between anxiety disorders and depression.