A prospective study of group cohesiveness in therapeutic horticulture for clinical depression.

This study aimed to assess changes in psychological distress and social participation in adults diagnosed with clinical depression during and after participating in a therapeutic horticulture programme, and to investigate if the changes covaried with levels of group cohesiveness during the intervention. An intervention with a single-group design was repeated with different samples in successive years (pooled n = 46). In each year, five groups of 3-7 participants went through the intervention. Data were collected before, twice during, and immediately after a 12-week therapeutic horticulture programme, as well as at 3-months' follow up. Mental health assessments included the Beck Depression Inventory, the State Subscale of Spielberger State-Trait Anxiety Inventory, the Positive Affect Scale from the Positive and Negative Affect Scale, the Perceived Stress Scale, and the Therapeutic Factors Inventory-Cohesiveness Scale. The analysis of the pooled data confirmed significant beneficial change in all mental health variables during the intervention. Change from baseline in depression severity persisted at 3-months' follow up. Increased social activity after the intervention was reported for 38% of the participants. The groups quickly established strong cohesiveness, and this continued to increase during the intervention. The average level of group cohesiveness correlated positively, but not significantly, with change in all mental health outcome variables.