Major depressive disorder (MDD).

What Is a Psychological Disorder?

What is the definition of a psychological disorder?
What does “abnormal” mean in psychology textbooks?

The short answer is: no one knows.

There is no universally agreed-upon definition of abnormality. However, there is a consensus among scientists:

A psychological disorder is a characteristic set of thoughts, feelings, and/or behaviors that cause distress and maladaptive functioning in society.

If it causes distress and makes someone maladaptive in their community, it may qualify as a psychological disorder.

But what if society itself is wrong?

Psychologists do not have a definitive answer.

Approaches to Psychopathology

There are two major approaches:

1. Biomedical approach

2. Psychosocial approach

Biomedical Approach

The biomedical approach argues that everything is biological:

• Genes

• Anatomy

• Neurochemistry

Psychosocial Approach

The psychosocial approach emphasizes:

• Psychology

• Sociology

• Environment

In other words: “It’s not you—it’s your surroundings.”

Example: Myocardial Infarction

Take myocardial infarction (MI)—death of heart muscle, commonly known as a heart attack.

• Angina = ischemic injury

• Myocardial infarction = cell death

A biomedical thinker says:

“MI is caused by a defect in cardiac muscle physiology.”

True-but incomplete.

A psychosocial thinker adds:

• Smoking

• Alcohol

• Diabetes

• Hypertension

• Stress

• Diet

• Corporate food practices

• Workplace stress

So what’s the truth?

Both are correct.

We have:

• Non-modifiable risk factors

• Modifiable risk factors

This leads us to the biopsychosocial model, which integrates:

• Biology (genes, anatomy)

• Psychology (thoughts, behaviors, emotions)

• Social factors (environment, class, stigma)

Classification of Psychological Disorders

Is there a reference that lists all psychological disorders?

Yes: DSM-5
(Diagnostic and Statistical Manual of Mental Disorders, 5th Edition)

Examples include:

• Psychotic disorders (e.g., schizophrenia, delusional disorder)

• Bipolar and related disorders

• Anxiety disorders

Historical Note

Historically, psychology focused on:

• Psychosis

• Neurosis

Today:

• Psychosis ≈ schizophrenia

• Neurosis ≈ anxiety disorders

Additional categories include:

• Obsessive-compulsive and related disorders

• Dissociative disorders

• Somatic symptom disorders

• Personality disorders (Clusters A, B, and C)

• Neurocognitive disorders (e.g., Alzheimer’s, Parkinson’s)

• Eating disorders

• Neurodevelopmental disorders

• Impulse-control disorders

• Sleep disorders

Today, we focus only on depressive disorders.

Types of Depressive Disorders

• Major Depressive Disorder (MDD)

• Persistent Depressive Disorder (PDD) (formerly dysthymia)

• Seasonal Affective Disorder (SAD)

  • Now called MDD with seasonal onset

“It was the spring of hope, it was the winter of despair.”
— Charles Dickens

Major Depressive Disorder vs Persistent Depressive Disorder

Feature	MDD	PDD
Duration	≥ 2 weeks	≥ 2 years
Severity	Severe	Mild to moderate
Urgency	High (life-threatening)	Chronic

Diagnostic Criteria: SIGECAPS

To diagnose MDD, you need:

• Depressed mood and/or loss of interest

• Five or more of the following symptoms

• Duration ≥ 2 weeks

SIGECAPS:

• S – Sleep disturbance

• I – Loss of Interest (anhedonia)

• G – Excessive Guilt

• E – Low Energy

• C – Poor Concentration

• A – Appetite change

• P – Psychomotor agitation or retardation

• S – Suicidal ideation

Patients often describe emptiness, not just sadness.

Diagnosis and Evaluation

Screening tools:

• PHQ-2

• PHQ-9

Rule out medical causes:

• TSH (hypothyroidism)

• Vitamin B12

• CBC (anemia, leukemia)

• CMP (liver and kidney disease)

Prognosis

Unfortunately, ~15% of patients with MDD may die by suicide if untreated.

This is why early recognition matters.

Treatment

Non-pharmacologic

• Lifestyle modification

• Cognitive Behavioral Therapy (CBT)

• Psychotherapy

• Electroconvulsive Therapy (ECT)

  • Especially useful in pregnancy or refractory depression

Pharmacologic

• Tricyclic antidepressants (older, cardiotoxic)

• SSRIs

• SNRIs

• MAO inhibitors (watch tyramine interactions)

• Atypicals:

  • Mirtazapine

  • Bupropion

  • Trazodone

  • Vilazodone

  • Vortioxetine

Advanced therapy:

• IV ketamine for refractory depression

Differential Diagnosis of Depressed Mood

• Normal stress response

• Major depressive disorder

• Persistent depressive disorder

• Adjustment disorder with depressed mood

  • Onset within 3 months of identifiable stressor.