This study will investigate the effects of aerobic exercise on mental states, cognition, and long-term outcomes in adolescents with subthreshold depressive and/or hypomanic syndromes and in non-clinical school children

Subthreshold depressive and hypomanic symptoms are common in adolescents, increasing the risk of developping into depression or bipolar disorder. Preliminary evidence shows that aerobic exercise might have positive effects in enhancing cognition and improving clinical symptoms in non-clinical and preclinical population and patients with mood disorders. This randomized controlled trial will investigate short-term (3 months) effects of aerobic exercise on cognition and clinical symptoms as well as the long-term (18 months) effects on the clinical outcomes of high-risk states.

Inclusion Criteria:

1. 2 or more DSM-IV defined depressive symptoms, with one as core symptoms ( lost interest or pleasure in activity or depressed mood), lasting for 1 week.
2. 2 or more DSM-IV defined manic symptoms, last for 4 days, but falling short of the criteria for hypomania; or meeting DSM-5 defined symptoms criteria for hypomania, lasting 2-3 days.
3. non-clinical subjects

Exclusion Criteria:

• DSM-IV defined major depressive disorder
• DSM-IV defined hypo/mania
• History of or current other Axis I Disorders
• Diagnosed neurological or musculoskeletal disorder/injury,
• Uncontrolled cardiovascular or metabolic diseases that are not suitable for running
• Diagnosed hypertension
• Other diagnosed serious medical conditions that are not suitable for cycling
• Severe suicidal ideation
• Mental retardation
• Currently participating in a exercise program or activity, defined as 30 minutes of vigorous physical activity 4-5 times per week