Types of Mental Health Disorders

Why This Matters

Mental health disorders represent one of the most significant public health challenges you'll encounter in Health and Wellness coursework. Understanding these conditions isn't just about memorizing symptoms—you're being tested on how disorders are classified, what mechanisms drive them, and how they impact biopsychosocial functioning. The DSM-5 (Diagnostic and Statistical Manual of Mental Disorders) organizes conditions by shared features, and exam questions frequently ask you to distinguish between disorders that look similar on the surface but differ in their underlying causes or treatment approaches.

As you study these disorders, focus on the diagnostic criteria, risk factors, and treatment modalities that define each category. Pay attention to how disorders within the same category share features but manifest differently. Don't just memorize symptoms—know what concept each disorder illustrates, whether that's mood dysregulation, anxiety response patterns, cognitive disruption, or behavioral compulsion cycles.

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Mood Disorders: When Emotional Regulation Breaks Down

Mood disorders involve persistent disturbances in emotional state that go far beyond normal fluctuations. The key mechanism is dysregulation of neurotransmitters like serotonin, dopamine, and norepinephrine, combined with structural and functional brain changes.

Major Depressive Disorder

• Persistent depressed mood lasting at least two weeks—characterized by sadness, hopelessness, and anhedonia (loss of interest or pleasure in activities)
• Neurovegetative symptoms include appetite changes, sleep disturbances, fatigue, and psychomotor changes that affect basic biological functions
• Cognitive impairment such as difficulty concentrating and indecisiveness can significantly impact academic and occupational performance

Bipolar Disorder

• Characterized by distinct manic and depressive episodes—mania involves elevated mood, decreased need for sleep, grandiosity, and risky behavior
• Episode patterns vary widely from rapid cycling (four or more episodes yearly) to years between mood shifts, making diagnosis challenging
• Mood stabilizers like lithium are first-line treatments, distinguishing bipolar management from typical depression treatment approaches

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Anxiety Disorders: The Fear Response Gone Awry

Anxiety disorders share a common thread of excessive fear or worry that's disproportionate to actual threat. The underlying mechanism involves hyperactivation of the amygdala and dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, creating a chronic stress response.

Generalized Anxiety Disorder

• Excessive worry about multiple life domains for at least six months—the worry is difficult to control and shifts between concerns about health, work, relationships, and daily matters
• Physical symptoms include muscle tension, restlessness, fatigue, and sleep difficulties resulting from chronic autonomic nervous system arousal
• Cognitive behavioral therapy (CBT) is highly effective, teaching patients to identify and challenge catastrophic thinking patterns

Panic Disorder

• Recurrent unexpected panic attacks—sudden surges of intense fear peaking within minutes, accompanied by physical symptoms like heart palpitations, sweating, and shortness of breath
• Anticipatory anxiety develops as individuals fear future attacks, often leading to agoraphobia (avoidance of situations where escape might be difficult)
• Distinguishing feature is the unexpected nature of attacks; they occur without obvious triggers, unlike phobia-related panic

Post-Traumatic Stress Disorder (PTSD)

• Develops following exposure to actual or threatened trauma—symptoms include intrusive memories, flashbacks, nightmares, and severe psychological distress at trauma reminders
• Four symptom clusters are intrusion, avoidance, negative alterations in cognition/mood, and hyperarousal (exaggerated startle response, hypervigilance)
• Trauma-focused therapies like EMDR (Eye Movement Desensitization and Reprocessing) and prolonged exposure are evidence-based treatments

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Obsessive-Compulsive and Related Disorders: The Compulsion Cycle

These disorders involve repetitive thoughts or behaviors that the individual feels driven to perform. The mechanism involves dysfunction in the cortico-striato-thalamo-cortical circuit, creating a loop where anxiety triggers compulsive behavior, which temporarily reduces distress but reinforces the cycle.

Obsessive-Compulsive Disorder (OCD)

• Obsessions are intrusive, unwanted thoughts that cause marked anxiety—common themes include contamination fears, need for symmetry, and forbidden thoughts
• Compulsions are repetitive behaviors performed to neutralize obsessions, such as excessive handwashing, checking, counting, or mental rituals
• Exposure and Response Prevention (ERP) is the gold-standard treatment, helping patients face feared situations without performing compulsions

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Psychotic Disorders: Disrupted Reality Processing

Psychotic disorders involve breaks from reality, including hallucinations and delusions. The dopamine hypothesis suggests that excessive dopamine activity in certain brain pathways contributes to positive symptoms, while reduced activity elsewhere may cause negative symptoms.

Schizophrenia

• Positive symptoms include hallucinations (most commonly auditory), delusions, and disorganized speech or behavior that represent additions to normal experience
• Negative symptoms involve deficits like flat affect, avolition (lack of motivation), and social withdrawal, which are often more disabling long-term
• Early intervention is critical—the longer psychosis goes untreated, the poorer the prognosis; antipsychotic medications target dopamine receptors

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Neurodevelopmental Disorders: Early-Onset Patterns

These disorders emerge during development and involve deficits in personal, social, academic, or occupational functioning. The underlying mechanisms typically involve differences in brain structure and function present from early childhood.

Attention-Deficit/Hyperactivity Disorder (ADHD)

• Three presentations exist—predominantly inattentive, predominantly hyperactive-impulsive, or combined; symptoms must be present before age 12
• Executive function deficits affect working memory, impulse control, and task organization, impacting academic performance and social relationships
• Stimulant medications like methylphenidate paradoxically improve focus by increasing dopamine and norepinephrine in the prefrontal cortex

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Eating Disorders: Distorted Body Image and Disordered Eating

Eating disorders involve severe disturbances in eating behavior and related thoughts and emotions. These disorders have the highest mortality rate of any mental illness, involving complex interactions between biological, psychological, and sociocultural factors.

Anorexia Nervosa

• Restriction of energy intake leading to significantly low body weight—accompanied by intense fear of gaining weight despite being underweight
• Distorted body image means individuals perceive themselves as overweight even when dangerously thin; this isn't simply vanity but a perceptual disturbance
• Medical complications include cardiac arrhythmias, bone density loss, and organ damage, making this one of the deadliest psychiatric conditions

Bulimia Nervosa

• Recurrent episodes of binge eating followed by compensatory behaviors—purging (vomiting, laxatives) or non-purging (fasting, excessive exercise)
• Individuals typically maintain near-normal weight, distinguishing bulimia from anorexia; shame and secrecy often delay treatment
• Electrolyte imbalances from purging can cause serious cardiac complications; dental erosion is a common physical sign

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Substance-Related Disorders: The Addiction Cycle

Substance use disorders involve continued use despite significant problems caused by the substance. The mechanism involves hijacking of the brain's reward circuitry, particularly dopamine pathways, creating powerful cravings and diminished response to natural rewards.

Substance Use Disorders

• Diagnostic criteria include tolerance, withdrawal, and loss of control—using more than intended, unsuccessful efforts to cut down, and continued use despite consequences
• Physical dependence vs. psychological addiction—physical dependence involves withdrawal symptoms; addiction encompasses compulsive drug-seeking behavior
• Evidence-based treatments include medication-assisted treatment (MAT) for opioid and alcohol use disorders, combined with behavioral therapies

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Quick Reference Table

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Self-Check Questions

1. Which two anxiety disorders both involve avoidance behaviors, and how do the triggers for avoidance differ between them?

2. A patient experiences periods of elevated mood, decreased need for sleep, and impulsive spending, followed by weeks of depression. Which disorder does this describe, and what distinguishes it from Major Depressive Disorder?

3. Compare and contrast the compulsive behaviors seen in OCD with the compulsive substance-seeking seen in addiction. What brain mechanism do they share?

4. If an FRQ asks you to explain why early intervention matters for mental health outcomes, which two disorders would provide the strongest examples and why?

5. Both anorexia nervosa and bulimia nervosa involve body image disturbance. What key behavioral and physical differences would help you distinguish between them on an exam?