By Catherine A. Sanderson, Amherst College
Different perspectives within the field of psychology differ in how they explain psychological disorders, which in turn lead to different types of treatment. But the most widely accepted explanation is that most psychological disorders are caused by some combination of biological, psychological, and environmental factors.
Environmental Factors
Some people will be at greater risk of developing any given disorder, due to their specific combination of all the factors that lead to such disorders. Disorders also vary considerably in the extent to which their causes are more genetic or more environmental.
One neurocognitive disorder that is often called post-concussion syndrome is clearly caused by a factor within the environment—traumatic brain injury, or TBI. This disorder is diagnosed when someone shows decline in their cognitive ability: memory, concentration, and processing speed immediately after having experienced some type of impact on the head. Also, the diagnosis requires that the impact must have resulted in a loss of consciousness, amnesia, or confusion.
Genetic Causes
In contrast, there is a strong genetic component to bipolar disorder, a mental health condition characterized by extreme mood swings, from intense highs (mania) to deep lows (depression). Evidence suggests that several genes contribute.
Having one biological parent with bipolar disorder leads to a 15% to 30% chance of developing it, which increases to 50% to 75% if both biological parents have it. Data from twin studies show that if one identical twin has bipolar, there’s an 85% chance their twin also has it.
On the other hand, these high percentages also suggest that environment still plays a role, even for this most genetically-based type of mental disorder.
Combinational Factors or the Diathesis-Stress Model
In fact, most evidence now suggests that mental illness results from a combination of biological, psychological, and environmental factors. This theory is known as the diathesis-stress model.
It proposes that psychological disorders develop from a predisposition to a given disorder based on biological, genetic, cognitive, and/or personality factors, which only manifests itself when combined with stressful conditions.
This article comes directly from content in the video series Introduction to Psychology. Watch it now, on Wondrium.
Schizophrenia and Its Symptoms
All of these factors influence whether someone develops schizophrenia, a group of severe psychotic disorders that influence a person’s thoughts, feelings, and behavior. Common symptoms of schizophrenia include disorganized and delusional thinking, disturbed perceptions such as hallucinations, and inappropriate emotions and actions. They may jump rapidly from one idea to the next, even within a single sentence, and show wildly inappropriate emotions, laughing when hearing about a loved one’s death, for example.
People with schizophrenia may see or hear things that aren’t there and often have false beliefs—known as delusions—of persecution or grandeur, such as believing the CIA is following them or that a voice inside their head is telling them to burn themselves with a cigarette lighter.
They have greater difficulty functioning in daily life or maintaining social relationships, given their loss of contact with reality. One well-known illustration of this disorder is seen in the movie A Beautiful Mind, a story about mathematician and Nobel Prize winner John Nash, who developed schizophrenia at the age of 30.
What Causes Schizophrenia?
Genes definitely play a role. One theory is that people with schizophrenia have an excessive number of receptors for dopamine, a neurotransmitter. This high level of receptors may intensify brain signals, so basically, they receive too much stimulation, which makes it hard for them to pay attention.
Another theory points to the fact that some people with schizophrenia show structural differences in particular parts of the brain.
Genetics and Schizophrenia
What is clear is that a person’s risk of developing schizophrenia increases if they have a relative with the disorder. Although only about 1% of people have schizophrenia, 10% of people who have a parent or sibling with schizophrenia develop this disorder, as do 50% of those who have an identical twin with schizophrenia.
So, genes matter, but genes aren’t the whole story. After all, even an identical twin with schizophrenia means only a 50-50 likelihood of that diagnosis for the other twin.
Environmental and psychological Factors
As for environmental and psychological factors that influence whether a person develops schizophrenia, the list begins with possible prenatal factors, such as maternal malnutrition, viral infections, or maternal stress. Factors may also include stressful living environments, such as poverty, trauma, abuse, or neglect, as well as substance use.
A psychotic disorder like schizophrenia is not very prevalent—it affects fewer than one out of a hundred people—but it leads to serious impairments in virtually all aspects of life. Estimates are that about 20% of people who are homeless meet the diagnostic criteria for schizophrenia.
Common Questions about Factors Affecting the Development of Psychological Disorders
Most evidence suggests that mental illness results from a combination of biological, psychological, and environmental factors. This theory is known as the Diathesis-Stress Model. It proposes that psychological disorders develop from a predisposition to a given disorder based on biological, genetic, cognitive, and/or personality factors, which only manifests itself when combined with stressful conditions.
Schizophrenia is a group of severe psychotic disorders that influence a person’s thoughts, feelings, and behavior. Common symptoms of schizophrenia include disorganized and delusional thinking, disturbed perceptions such as hallucinations, and inappropriate emotions and actions.
A person’s risk of developing schizophrenia increases if they have a relative with the disorder. Although only about 1% of people have schizophrenia, 10% of people who have a parent or sibling with schizophrenia develop this disorder, as do 50% of those who have an identical twin with schizophrenia.
