More than 500 charitable and voluntary organisations in the UK offer emotional support, known as 'befriending', to patients in the community.
Researchers from the University of Manchester reviewed 24 randomised controlled trials on emotional support interventions. The trials looked at more than 4,000 vulnerable people, included new mothers, people recently bereaved or with chronic illnesses.
Emotional support led to a significant reduction in depressive symptoms in people receiving no other treatment.
It is thought befriending increases patients' perceived level of social support, boosting their ability to cope with stress.
The researchers did not find evidence to demonstrate this, but they said befriending could cut absenteeism from work by extending patient choice and offer a less 'medicalised' approach to managing low-level depression in the community.