Although we continued to intensively investigate the causes and treatments of winter depression, no new studies of summer depression have been carried out during the past year. Thermoregulation and thyroid axis function, which were the focus of our hypotheses about triggers and pathogenic mechanisms of summer depression, continue to be investigated in connection with our project on the therapeutic mechanisms of sleep deprivation (ZO1 MH 02424-02 CP). Owing to competing priorities, we do not expect to conduct any further studies of summer depression in the near future. Therefore, Project Z01 MH 02402-02 has been terminated.