These Are the Potential Causes of Schizophrenia

Summary

Dr. Dominic Sportelli explains that schizophrenia is a neuropsychiatric developmental disorder involving brain function, but there is no single known cause. Its causes are complex and not fully understood. Genetic and environmental influences may interact, and several risk factors may combine to create what Dr. Sportelli calls a “perfect storm.” The figures and associations discussed are based on research; they do not mean that any one factor inevitably leads to schizophrenia.

Genetics and family history

Genetics is described as an important risk factor, suggesting an underlying biological component. Dr. Sportelli cites these approximate comparisons:

• The general-population likelihood is about 1%.
• If one identical twin has schizophrenia, the other twin’s likelihood is about 50%.
• If both parents have schizophrenia, the likelihood for their child is about 40%.
• Having a sibling or one parent with schizophrenia raises the likelihood by about 10% compared with the baseline.

These figures indicate increased risk, not certainty. Even among identical twins, both do not always develop the condition.

Substance use and psychosis

Psychosis is a symptom that can involve disorganized thinking, hallucinations, delusions, or altered perception. It is not the same thing as schizophrenia.

Some substances can bring on substance-induced psychosis. Symptoms sometimes persist after a drug’s effects have worn off, making it difficult to determine whether the substance caused the psychosis or revealed an existing vulnerability.

Substances emphasized as potential risks include:

• Cannabis, particularly when used during adolescence, while the brain is still developing. The doctor cites studies reporting a four- to sixfold increase in the likelihood of later schizophrenia among some users.
• Hallucinogens, including LSD, psilocybin, mescaline, and peyote.
• Amphetamines and other stimulants, especially when used at high doses over a long period.

The discussion describes a “double-hit” hypothesis: a person with a genetic predisposition or major environmental stressor may be more vulnerable to psychosis or schizophrenia-like symptoms following substance use.

Other substances, including alcohol, can also contribute to psychiatric symptoms, especially when used heavily or during withdrawal. These effects may include paranoia, delusions, mania, or severe depression.

Kyle shares an anecdote about an acquaintance who developed severe, persistent psychotic symptoms after substance use. The speakers note that the person’s prior vulnerability and the role of the substances cannot be determined from the story, but that substance use did not help.

Other environmental and developmental risk factors

The interview identifies several factors associated with increased risk, while emphasizing that none alone establishes a cause:

• Adverse childhood experiences, including serious trauma, abuse, or neglect.
• Birth in winter or spring, an epidemiological association whose explanation is uncertain. One proposed theory involves viral exposure during pregnancy or early infancy.
• Prenatal or birth-related factors, such as low birth weight and complications.
• Malnutrition, including conditions associated with famine.
• Hypoxia, or a period of inadequate oxygen reaching the brain.

Dr. Sportelli frames these as possible contributors to disrupted early brain development and emphasizes that risk may arise through combinations of influences.

Hope, treatment, and stigma

Dr. Sportelli cautions against treating schizophrenia as synonymous with “madness” or assuming that people diagnosed with it cannot live well. He emphasizes that schizophrenia affects a minority of the population, effective treatments are available, and families and loved ones should not lose hope.

In a closing example, Kyle contrasts how people may respond to someone expressing suicidal thoughts with how they respond to someone showing signs of psychosis. Dr. Sportelli identifies fear and stigma as reasons people may help one person but avoid another, and stresses that people experiencing psychosis also need compassion and support.

Speakers and sources featured

• Kyle Kittleson, MedCircle host. (The subtitles render his name inconsistently.)
• Dr. Dominic “Dom” Sportelli, psychiatrist.
• Research evidence referenced by Dr. Sportelli: Twin studies and epidemiological data; no individual study or outside researcher is named.
• An unnamed acquaintance appears in Kyle’s anecdote but does not speak in the video.