Historical and Modern Perspectives on Psychological Disorders
Supernatural Causes
For most of human history, people explained mental illness through supernatural forces. Ancient cultures attributed psychological disturbances to demonic possession, curses, or punishment from the gods.
- Trephination involved drilling holes in the skull to release evil spirits thought to cause mental disturbances, headaches, or seizures. This is one of the earliest known "treatments" for psychological disorders.
- During the Middle Ages, psychological disorders were frequently linked to witchcraft. Common responses included exorcisms, prayer, and fasting.
These explanations have been replaced by scientific approaches, but they're worth knowing because they show how dramatically our understanding has shifted.
Biological and Psychological Origins
Modern perspectives split into two broad camps: biological and psychological. Most psychologists today recognize that both matter.
Biological perspectives focus on genetics, brain chemistry, and brain structure as the roots of psychological disorders.
- Imbalances in neurotransmitters like serotonin and dopamine are linked to conditions such as depression and schizophrenia. For example, the dopamine hypothesis suggests that excess dopamine activity contributes to schizophrenia symptoms.
- Structural brain abnormalities also play a role. People with schizophrenia, for instance, sometimes show enlarged ventricles or reduced hippocampal volume on brain scans.
Psychological perspectives emphasize how early experiences, learned behaviors, and thought patterns contribute to mental disorders. There are three major schools of thought here:
- Psychodynamic theories (rooted in Freud) suggest that unresolved unconscious conflicts can surface as psychological symptoms. Concepts like repression and fixation fall under this umbrella.
- Behavioral theories propose that maladaptive behaviors are learned through conditioning and reinforcement. A phobia, for example, might develop after a person associates a neutral stimulus with a frightening experience (classical conditioning) and then avoids it repeatedly (operant conditioning).
- Cognitive theories focus on how distorted thinking patterns affect mental health. Someone prone to catastrophizing (assuming the worst possible outcome) or overgeneralization (drawing broad conclusions from a single event) may be more vulnerable to depression and anxiety.
Genetic Heritability
Genes don't guarantee you'll develop a disorder, but they can significantly raise your risk. Researchers measure this using heritability estimates, which describe how much of the variation in a trait across a population can be attributed to genetic differences.
- Schizophrenia has a heritability estimate of roughly 80%. First-degree relatives of someone with schizophrenia are about 10 times more likely to develop it than the general population.
- Bipolar disorder has a heritability estimate of around 70–80%. Monozygotic (identical) twins show a 40–70% concordance rate, while dizygotic (fraternal) twins show only 5–10%. That gap is strong evidence for a genetic component.
- Autism spectrum disorder (ASD) has a heritability estimate of 50–90%. Siblings of individuals with ASD have a 2–18% chance of also having the disorder, compared to about 1% in the general population.
The twin study comparison is especially useful for exams: a large difference in concordance rates between identical and fraternal twins points toward genetic influence, since identical twins share nearly 100% of their DNA while fraternal twins share about 50%.
Diathesis-Stress Model
The diathesis-stress model ties everything together. It proposes that psychological disorders result from an interaction between a predisposition (the diathesis) and environmental stressors.
- Diathesis refers to a vulnerability, whether genetic, biological, or psychological, that makes someone more susceptible to a disorder. This could be a family history of depression, a neurochemical imbalance, or certain personality traits.
- Stress refers to life events or chronic adversities that can trigger symptoms, such as losing a loved one, financial hardship, or ongoing trauma.
The key idea: someone with a high diathesis needs relatively little stress to develop a disorder, while someone with a low diathesis might withstand significant stress without developing one. Think of it as a threshold. Everyone has some level of vulnerability, but not everyone encounters enough stress to push them past that threshold.
This model explains a question students often ask: why do some people develop mental illness after a stressful event while others in the same situation don't? The answer lies in the interaction between their individual vulnerability and the stress they experience. It's a clear example of the nature-and-nurture interplay that runs throughout psychology.