Schizophrenia is a severe type of mental illness that affects a person’s thoughts, perceptions, and behaviors. Researchers estimate up to 1 percent of adults worldwide have schizophrenia.

What exactly causes schizophrenia is still unclear. However, we do have some ideas about the various factors that may be involved. One of these is dopamine. It’s a type of brain chemical messenger called a neurotransmitter.

Experts believe that changes in dopamine activity may contribute to certain schizophrenia symptoms. This is called the dopamine hypothesis of schizophrenia. Keep reading below as we explore this concept in more detail.

Dopamine is a type of neurotransmitter. Neurotransmitters are brain chemical messengers that help your nerve cells communicate with one another.

Different neurotransmitters attach (bind) to different receptors on nerve cells. When a neurotransmitter binds to the right receptor on a nerve cell, it triggers that cell to take a specific action. Think of it like a key in a lock.

Different neurotransmitters are associated with many physical and psychological processes in the body. For example, dopamine is involved in things like:

  • motivation and reward
  • movement
  • mood
  • attention, learning, and memory
  • sleep and dreaming

Neurotransmitters travel along neuronal pathways, which are basically long chains of nerve cells (neurons) that help different parts of the brain talk with one another.

Some pathways that appear to be associated with schizophrenia symptoms have been identified. These pathways use dopamine as their primary messenger, and include the mesolimbic pathway and the mesocortical pathway.

We’ll discuss the role these pathways may have in different schizophrenia symptoms a little later.

The dopamine hypothesis of schizophrenia has been around for a long time. In fact, it was first proposed in the 1960s.

During this time, doctors noticed that an antipsychotic drug called chlorpromazine, which reduces dopamine activity, effectively treated some types of schizophrenia symptoms.

Due to this observation, doctors and researchers theorized that increased levels of dopamine in the brain contributed to some symptoms of schizophrenia. But it’s a little more complicated than that.

High levels of dopamine don’t cause schizophrenia symptoms. The role dopamine plays in schizophrenia is more complex than that and involves specific dopamine activity.

Over time, researchers have discovered evidence that isn’t in line with the original dopamine hypothesis of schizophrenia. For example, they found that some people with schizophrenia had typical levels of dopamine in their cerebrospinal fluid as opposed to elevated levels.

Further, researchers found that other antipsychotic drugs that do not block the effects of dopamine could still treat symptoms of schizophrenia.

Some schizophrenia symptoms may be triggered when certain areas of the brain have high levels of dopamine activity while others have lower levels of activity.

Other neurotransmitters and schizophrenia

Doctors and researchers have found that dopamine isn’t the only neurotransmitter involved in schizophrenia. Other neurotransmitters in the brain are also likely involved in some way.

An example of this is glutamate. This neurotransmitter is important for things like learning, memory, and mood. Glutamate travels along a pathway that links several regions of the brain that may be important in schizophrenia.

Glutamate first came on the radar when it was found that inhibiting a certain type of glutamate receptor, called an NMDA receptor, led to schizophrenia-like symptoms.

Other neurotransmitters that may also be involved in schizophrenia include gamma-aminobutyric acid (GABA) and serotonin.

Schizophrenia causes

In addition to what we’ve discussed already, several other factors are believed to be involved in the development of schizophrenia:

  • Genetics. Schizophrenia can run in families, although the exact genes involved are still unclear.
  • Brain structure. Compared with people without schizophrenia, those with schizophrenia can have slight changes in their brain structure.
  • Complications during pregnancy and birth. Some complications that happen during pregnancy and birth, such as low birth weight and maternal malnutrition, have been associated with increased schizophrenia risk.
  • Environmental factors. It’s thought that factors like experiencing trauma or using certain types of drugs may help trigger schizophrenia in people who are at risk of the condition.

Overall, schizophrenia is a very complex condition. As such, it’s likely that an intricate combination of biological, genetic, and environmental factors play a role in causing it.

Doctors still don’t know exactly how dopamine relates to schizophrenia symptoms, but there are theories. Aberrant salience is another theory tied to schizophrenia and dopamine.

But what exactly is salience in the first place?

Generally speaking, salience is how your brain attaches importance to something. For example, when you’re crossing the street, cars are your most salient thought.

Researchers are investigating whether increased dopamine levels in the mesolimbic pathway may lead to problems with salience.

When salience is dysfunctional, someone crossing the street may pay little attention to cars because their brain is telling them it’s more important to pay attention to the birds flying overhead.

This theory can help explain some of the more noticeable symptoms of psychosis.

Below, we’ll explore the three categories of schizophrenia symptoms and discuss the potential of dopamine involvement.

Positive symptoms

Dopamine is most closely linked to positive symptoms of schizophrenia. Positive symptoms include:

  • Hallucinations. This involves perceiving things that aren’t actually there. Hearing voices is the most common example.
  • Delusions. These are strongly held beliefs that are untrue and may not seem logical to other people.
  • Unusual speech patterns. This can include things like suddenly stopping in the middle of talking about something, moving quickly from topic to topic, or making up words.
  • Atypical body movements. This may include things like repeating the same motion over and over again.
  • Disordered thinking. This is a disordered way of thinking that can result in confusion and unusual behavior.

Remember the antipsychotic drugs we talked about earlier?

These actually work by blocking specific dopamine receptors. Blocking these receptors reduces positive schizophrenia symptoms but has little effect on other symptoms.

Positive symptoms have been linked to increased dopamine activity in the mesolimbic pathway. This is one of the major dopamine-related pathways in the brain.

Negative and cognitive symptoms

The negative symptoms of schizophrenia can include:

  • apathy or disinterest in daily activities
  • limited emotional expression
  • avoiding social interactions
  • trouble with planning or following through with plans
  • low energy levels

People with schizophrenia can also have cognitive symptoms, which can include issues with things like:

  • learning and memory
  • concentration
  • attention
  • decision making

Decreases in dopamine activity in certain areas of the brain may lead to the negative and cognitive symptoms of schizophrenia. The pathway thought to be affected by this is called the mesocortical pathway.

The mesocortical pathway is another one of the major dopamine-related pathways in the brain. Messages sent along this pathway go to the prefrontal cortex. This is an area of the brain associated with processes like:

  • decision making
  • memory
  • attention
  • motivation
  • emotional control

Note that the processes above are those that are largely affected by negative and cognitive symptoms of schizophrenia. As such, it makes sense that reduced dopamine activity along this pathway may contribute to these symptoms.

Dopamine plays an important role in the treatment of schizophrenia. Antipsychotic drugs block dopamine activity and are used to manage the positive symptoms of schizophrenia.

However, people taking antipsychotic drugs often experience side effects. These can include:

The exact side effects a person may experience can vary based on the specific antipsychotic drug that’s used. Often, lowering the dose or switching to a different drug can reduce side effects.

Another downside is that antipsychotic drugs don’t help nearly as much with negative and cognitive symptoms. These types of symptoms are typically managed with one or a combination of the following psychosocial treatments:

There’s currently no cure for schizophrenia, but it can be successfully managed. It’s a chronic (long lasting) condition that requires treatment over the course of a person’s lifetime.

Researchers continue to investigate the role of dopamine in schizophrenia. This is not only important in further understanding the causes of schizophrenia itself, but also in improving treatment.

Current antipsychotic drugs are mostly effective for positive symptoms. Even then, some cases of schizophrenia can be resistant to these drugs. Further, antipsychotic drugs can come with significant side effects, particularly when they’re used long term.

Understanding how dopamine and other neurotransmitters affect schizophrenia can help researchers develop newer treatments that:

  • are more effective overall
  • target neurotransmitters other than dopamine
  • help address negative and cognitive symptoms
  • have fewer side effects

Increases in dopamine activity in certain parts of the brain can contribute to the positive symptoms of schizophrenia. Meanwhile, reduced dopamine activity in other parts of the brain may affect negative and cognitive symptoms.

Dopamine is just one of many factors involved in schizophrenia symptoms. Other neurotransmitters and various physical, genetic, and environmental factors are also important.

The antipsychotic drugs currently in use primarily target dopamine and can help manage positive symptoms of schizophrenia, but not others.