Severity level of mental disorders

Spectrum of severity 

🔍 What we can quantify:

Epidemiological studies — especially from the WHO World Mental Health Surveys and NIMH (U.S. National Institute of Mental Health) — often divide serious mental illness (SMI) into:

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⚖️ Severity Levels (based on impairment and need for care)

1. Severe (5–7% of population)

Chronic, disabling, and typically requires long-term care.

Examples:

Schizophrenia

Bipolar I disorder with psychosis

Severe major depressive disorder (e.g. suicidal, psychotic, or recurrent episodes)

Severe autism spectrum disorder

Features:

Often unemployed or on disability

Requires hospitalization or long-term medication

Poor quality of life

Estimated prevalence: 5–7% lifetime

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2. Moderate (10–15% of population)

Causes significant suffering and functional limitation, but not fully disabling.

Examples:

Moderate depression or anxiety

Bipolar II disorder

ADHD with school/work impact

PTSD or OCD that interferes with life but allows some functioning

Features:

Can hold a job or attend school with difficulty

Likely needs treatment

Estimated prevalence: 10–15% lifetime

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3. Mild or Transient Disorders (30–35% of population)

Short-term, self-limiting, or mild symptoms.

Examples:

Mild adjustment disorder

Situational depression/anxiety

Phobias that don’t impair functioning

Features:

Often underdiagnosed or untreated

May recover without intervention

Estimated prevalence: 30–35% lifetime

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🧮 Combined View (approximate lifetime prevalence):

Severity Disorders included Lifetime prevalence

Severe Psychosis, severe bipolar, disabling MDD, severe autism 5–7%

Moderate Moderate depression, PTSD, bipolar II, OCD 10–15%

Mild Situational anxiety, mild phobias 30–35%

Total (any) All diagnosable disorders ~50%

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📘 Sources:

WHO World Mental Health Survey Initiative

National Comorbidity Survey Replication (NCS-R), U.S.

Institute for Health Metrics and Evaluation (IHME) – Global Burden of Disease

Kessler RC et al. studies on prevalence and severity in JAMA, Lancet Psychiatry

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