Schizophrenia and Genetics

Schizophrenia is a complex mental health disorder that affects how a person thinks, feels, and behaves. People living with schizophrenia may have difficulty distinguishing between what is real and what is not. Because the symptoms are so serious, researchers have spent decades trying to understand what causes schizophrenia. One of the most important questions is whether schizophrenia is genetic.

Schizophrenia Defined

Schizophrenia is a severe and chronic mental health disorder classified as a form of psychosis. While it can affect anyone, it typically begins in late adolescence or early adulthood ^[1].

Schizophrenia significantly disrupts thinking, perception, and behavior, often causing a significant detachment from reality. The disorder also shortens lives. Studies show that in all age groups, people diagnosed with schizophrenia live approximately 20 years less than the general population ^[2]. In short, the life expectancy when diagnosed with schizophrenia varies, but in some cases, it leads to premature death.  

Symptoms of Schizophrenia

The symptoms of schizophrenia can vary widely from one person to another. They often include behavioral changes and cognitive disruptions that affect daily functioning and quality of life ^[1].

Common behavioral symptoms of schizophrenia include:

• Delusions: Paranoid beliefs that are not based on reality.
• Hallucinations: Sensing things that are not present, such as hearing voices or seeing things that do not exist.
• Disorganized thinking (speech): Speech that is jumbled, difficult to follow, or disconnected from the topic.
• Extremely disorganized or abnormal motor behavior: Includes unpredictable actions, such as childlike silliness, aggression, resistance to instructions, or inappropriate behavior.
• Negative symptoms: Reduced emotional expression, motivation, and ability to engage in daily activities.

Cognitive challenges related to schizophrenia can affect learning, memory, and decision-making and may include:

• Poor memory: Difficulty recalling recent or short-term information.
• Trouble concentrating: Inability to stay focused on tasks.
• Impaired executive functioning: Problems organizing thoughts, planning, or making decisions.
• Slow processing speed: Taking longer to understand or respond to information.
• Reduced problem-solving ability: Difficulty analyzing situations and identifying solutions.
• Difficulty learning new information: Trouble absorbing and applying new knowledge.

Changing Views on Subtypes

Schizophrenia was once categorized into subtypes, such as disorganized, catatonic, and paranoid schizophrenia, based on presenting symptoms. However, these subtypes often overlapped and made diagnosis less reliable. To improve accuracy and reflect the complexity of the disorder, the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) has removed these subtype categories ^[3]. Schizophrenia is now viewed as a single disorder with a wide range of possible symptom presentations.

The Role of Genetics in Schizophrenia

Understanding what schizophrenia is and how it affects thoughts, emotions, and behavior lays the groundwork for exploring its potential causes. While the exact cause remains unknown, experts believe schizophrenia results from a complex interplay of environmental influences, imbalances in brain chemistry, and genetics. 

Family and Twin Studies

Some of the earliest evidence suggesting a genetic link comes from family and twin studies ^[4]. If one identical twin has schizophrenia, the other twin has about a 50% chance of developing it too. In contrast, fraternal twins, who share only about half of their genes, have a lower possibility of both having the disorder. This difference supports the idea that genes are involved.

Research indicates that having a first or second-degree relative, such as a parent or grandparent, with schizophrenia significantly increases the risk of developing the disorder ^[5]. Substantial hereditary risks of schizophrenia appear to exist, showing that the disorder often clusters within families. This suggests shared genetic factors contribute to the disorder’s complexity, emphasizing the importance of family history in assessing risk.

Specific Genes and Risk Factors

Recent advances have allowed scientists to study the DNA of thousands of people with and without schizophrenia. Genome-wide association studies (GWAS) investigate the biological basis of different diseases and reveal many small changes in genes that are more common in people with schizophrenia ^[5].

One example is the COMT gene, which helps control dopamine, a chemical in the brain. Variations in the COMT gene may affect how the brain processes information and responds to stress, both of which are important in schizophrenia. Another example is the DISC1 gene, which is linked to brain development and function. Although no single biological basis of schizophrenia exists, scientists believe that having certain versions of many genes can increase a person’s risk ^[6].

Environmental and Other Influences

Even though family history and schizophrenia risk are linked, this is not the only factor. Most people who have a genetic risk for schizophrenia do not develop the disorder. This means that other influences such as environental and genetic factors are also important.

Environmental Factors

Environmental factors such as stress, trauma, or drug use can contribute to the development of schizophrenia. For example, using cannabis during the teenage years, especially in large amounts, has been linked to a higher risk of schizophrenia in people who are already vulnerable ^[7].

Pregnancy and birth complications, such as infections or lack of oxygen at birth, may also raise the risk of schizophrenia later in life ^[8].

Gene-Environment Interaction

Scientists believe that schizophrenia develops when both genetic and environmental risks are present. This concept is called the “diathesis-stress model.” In this model, a person may inherit a vulnerability to the disorder, but it only appears when certain stressors or life events trigger it ^[9].

This explains why two people with the same genetic risk might have very different experiences. One person may develop schizophrenia, while the other does not, depending on the environment and life events.

Supporting Loved Ones with Schizophrenia

Understanding schizophrenia’s genetic vs. environmental causes and how they are interconnected is both helpful and concerning for families. On one hand, it can bring relief to know that the illness is not caused by a single gene or solely by environmental factors. On the other hand, it may raise worries about things outside of the family’s control or whether other family members are at risk of developing the disorder. These concerns naturally lead to an important question: What steps, if any, can a family take to reduce the risk of schizophrenia?

Reducing Risk

The hereditary risks of schizophrenia are not always clear.  However, certain lifestyle choices and supportive environments may help reduce the risk or lessen the severity of the illness. While these factors cannot guarantee prevention, they can promote overall mental well-being and support early intervention, which is valuable for improving outcomes.

Some strategies that may help to reduce the risk of or address schizophrenia include:

• Avoid drug and alcohol use: Substance use can raise the risk or worsen symptoms.
• Manage stress: Healthy routines and coping skills help reduce triggers.
• Early mental health care: Addressing symptoms early can improve long-term outcomes.
• Encourage healthy habits: Good sleep, diet, and activity levels support brain health.

Families can also support loved ones by learning about schizophrenia’s genetic vs. environmental causes, reducing stigma associated with historical misconceptions about schizophrenia, and encouraging treatment and healthy habits. Education and understanding can make a big difference in how a person who is diagnosed with schizophrenia copes with the disorder. 

Navigating Life with Schizophrenia

Schizophrenia is a serious mental health condition that affects thoughts, emotions, and behaviors. While the exact cause is still unknown, genetics is understood to play a role. 

However, genes alone do not cause schizophrenia. Environmental factors and life experiences also matter. The most accurate way to understand schizophrenia is to see it as the result of many influences working together.

For families and individuals affected by this illness, knowing about the hereditary risks of schizophrenia can help reduce blame and encourage compassion. Ongoing efforts offer hope for better treatments and support in the years to come.