Key Points

Abnormal behavior is generally characterized by four key features, often called the 'four Ds': Deviance (unusual), Distress (unpleasant), Dysfunction (interfering with daily life), and Danger (to oneself or others).

There are two main views on abnormality. The first considers it a deviation from social norms, while the second, more widely used view, defines it as maladaptive behavior that interferes with the well-being of the individual.

Historically, abnormal behavior has been explained by three recurring perspectives: the supernatural (evil spirits), the biological or organic (bodily or brain dysfunction), and the psychological (flaws in thinking or feeling).

This modern interactional approach suggests that psychological disorders are caused by a combination of biological factors (genes, neurotransmitters), psychological factors (stress, trauma), and socio-cultural factors (family, societal norms).

Two primary systems are used to classify psychological disorders. The American Psychiatric Association (APA) publishes the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), while the World Health Organization (WHO) uses the International Classification of Diseases (ICD-10).

This model explains that a psychological disorder develops when a person with a pre-existing vulnerability or predisposition (diathesis) encounters a stressful situation that triggers the onset of the disorder.

Anxiety disorders are characterized by excessive and persistent fear, anxiety, and related behavioral disturbances. Key types include Generalized Anxiety Disorder (GAD), Panic Disorder, Phobias, and Separation Anxiety Disorder.

OCD involves obsessions, which are intrusive and unwanted thoughts, and compulsions, which are repetitive behaviors (like checking or cleaning) performed to reduce the anxiety caused by the obsessions.

These disorders develop after experiencing a traumatic or stressful event. Post-Traumatic Stress Disorder (PTSD) is a prominent example, with symptoms like flashbacks, nightmares, and emotional numbing.

Somatic symptom disorders involve physical complaints without a medical cause. Dissociative disorders feature a disruption in consciousness, memory, or identity, such as in dissociative amnesia or dissociative identity disorder.

Major Depressive Disorder is marked by a persistent low mood and loss of interest or pleasure. Bipolar Disorder involves alternating episodes of mania (elevated mood and energy) and depression.

Positive symptoms of schizophrenia represent an excess or distortion of normal functions. They include delusions (false beliefs), hallucinations (false sensory perceptions), and disorganized thinking and speech.

Negative symptoms reflect a loss or deficit in normal functioning. Key symptoms are alogia (poverty of speech), blunted affect (reduced emotional expression), and avolition (loss of motivation).

These disorders manifest early in development, often before school age. They include Attention-Deficit/Hyperactivity Disorder (ADHD), Autism Spectrum Disorder, Intellectual Disability, and Specific Learning Disorder.

These are characterized by severe disturbances in eating behavior. Anorexia Nervosa involves intense fear of gaining weight and self-starvation, while Bulimia Nervosa involves cycles of binge eating followed by purging.

This category includes disorders related to the abuse of drugs such as alcohol, cocaine, and heroin. These lead to maladaptive behaviors and significant impairment in social and occupational functioning.

Various models explain the psychological causes of disorders. These include the psychodynamic (unconscious conflicts), behavioural (faulty learning), cognitive (irrational thoughts), and humanistic-existential (issues of self-actualization and meaning) models.

Imbalances in brain chemicals called neurotransmitters are linked to specific disorders. For example, low activity of GABA is associated with anxiety, excess dopamine with schizophrenia, and low serotonin with depression.