Background: Longitudinal caregiver studies of patients with mood disorders report no consistent pattern in burden over time. This naturalistic study of caregivers of patients with mood disorders assesses caregiver perceptions of burden, reward and family functioning at hospitalization and at 1 year follow-up, Methods: Thirty-nine caregivers of patients with mood disorders were recruited during their relative's in-patient psychiatric hospitalization. Caregivers were given an assessment packet to complete at the time of enrollment and identical assessment packets were mailed to the caregivers at 1 year. Results: Caregivers of bipolar disorder relatives reported less reward, more subjective burden and worse family functioning than depression caregivers, at recruitment. Bipolar caregivers showed a significant reduction in burden 1 year after their relative was discharged from the hospital, whereas depression caregivers showed no change at 1 year. At 1 year, overall family functioning was unchanged and was in the unhealthy range in all dimensions except for behaviour control. Limitations of the study include the small sample size, the selective recruitment from a hospital setting where family members did not actively seek out help and the high drop-out rate. Conclusions: Caregivers of relatives with mood disorders show a different pattern of burden and reward, over time, depending on the patient diagnosis. In all cases, however, family functioning was significantly impaired. Clinical relevance: Short-term family interventions can be offered at the time of hospitalization to try to reduce caregiver burden and increase caregiver reward. (C) 2004 Published by Elsevier B.V.