Assessment tools
Forty studies included in this systematic review used a self-reporting validated outcome measurement tool and two studies performed a structured diagnostic interview for reporting either depressive or anxiety symptoms or both. Five studies reported a depression or anxiety disorder based on medical records (ICD-9 diagnoses). Various outcome measures were used of which the details are listed in appendixS4 [74-93]. With regard to the assessment of depressive symptoms, the Hospital Anxiety and Depression Scale (HADS) or Becks Depression Inventory (BDI) were most frequently used [76,83]. Concerning assessment of anxiety symptoms, the most commonly used tools were the HADS or the State-Trait Anxiety Inventory (STAI) [83,92]. Assessment of anxiety symptoms included the evaluation of either general, state, trait and/or phobic anxiety. Instruments developed for the global assessment of anxiety focus on the assessment of mood, cognition and behaviour, whereas tools for assessing phobic anxiety more often include somatic symptoms of anxiety [94]. State anxiety questionnaires evaluate anxiety as a current emotional state, whereas trait anxiety questionnaires evaluate individual differences in anxiety as a personality trait [95].