Direct assessment of improvement in winter depression with a visual analogue scale: high reliability and validity

Reliability and validity of direct visual analogue scale (VAS) ratings of improvement were assessed in 162 patients with Seasonal Affective Disorder, Winter Depression type (W-SAD), after light treatment for 6 consecutive days. The patients were rated with the Montgomery-Asberg Depression Rating Scale (MADRS) and a scale for the 'atypical' symptoms hypersomnia, hyperphagia and carbohydrate craving (the ATYP scale) before and after treatment. After treatment the patients also self-rated their global improvement on a 10-cm VAS, with anchoring points of 'No improvement' and 'Complete improvement'. VAS ratings were repeated several times, with 1-4 weeks between assessments, in a follow-up period, always referring to improvement in relation to baseline, and accompanied by a statement whether there had been any change since the former VAS rating. Shortly after treatment there was a mean reduction of 59.8% on the MADRS and 57.1% on the ATYP score, and 58.4% improvement as measured by the VAS. VAS rating correlated highly with percentage reduction of MADRS scores (r=0.85) and somewhat less with reduction of ATYP scores (r=0.64). VAS ratings in the follow-up period showed an extremely high test-retest reliability (r=0.96) for two consecutive ratings between which the patient stated that there had been no definite change. The results support the use of VAS ratings for assessment of global improvement after light treatment in patients suffering from W-SAD; use in other kinds of depression and with other types of treatment remains to be explored.