## TL;DR
Mental health encompasses emotional, psychological, and social well-being. The biopsychosocial model recognizes mental disorders arise from genetic vulnerability, neurobiological dysfunction, psychological factors, and social determinants.

## Core Explanation
Major categories: mood disorders (depression, bipolar), anxiety disorders, psychotic disorders (schizophrenia), trauma-related disorders (PTSD), neurodevelopmental disorders (ADHD, autism). Evidence-based treatments combine pharmacotherapy with psychotherapy (CBT, DBT).

## Detailed Analysis
The monoamine hypothesis guided antidepressant development for decades; newer research emphasizes neuroplasticity, inflammation, and HPA axis dysregulation. Ketamine's rapid antidepressant effects (within hours vs. weeks for SSRIs) demonstrated glutamatergic NMDA receptor modulation as a novel mechanism.

## Further Reading
- NIMH: Mental Health Information
- The Lancet Psychiatry
- APA: Practice Guidelines