Causes of a mood disorder - neurobiological influences

1) Neurotransmitter system: serotonin and its relation to other neurotransmitters (eg noradrenaline and dopamine), associated with a lack of serotonin. Permissive hypothesis - low serotonin permits other neurotransmitters to vary wildly increasing vulnerability. 2) Endocrine system: elevated cortisol; decrease neurogenesis in the hippocampus.