First-line treatments for mood disorders do little to improve cognitive and general functioning, and impairment in these areas is related to long-term relapse. This study will examine whether the addition of a therapy targeting cognitive function (cognitive remediation; CR), to an evidence-based psychotherapy (Interpersonal and Social Rhythms Therapy; IPSRT), is effective in reducing long-term relapse rates in mood disorders. Ninety patients with major depressive disorder or bipolar disorder, recently discharged from Specialist Mental Health Services in Canterbury, will be recruited and randomised to receive IPSRT alone, or in combination with a group-based CR programme. The treatment period for both intervention arms will be 12 months. The primary outcome in this study will be relapse rates into mood episodes in the 12 months following the end of treatment. Other outcomes, which will be assessed at treatment-end and 12 months after treatment-end, will include cognitive and general functioning.