Brain chemicals can play a role in mood and some behaviors. The dopamine hypothesis of schizophrenia is a prime example.

Many things contribute to your defining characteristics.

Childhood experiences, genetics, and the level of chemicals in your brain all influence what makes you, you.

Some experts believe that neurochemical imbalances may be the underlying cause of many mental health conditions.

When it comes to living with a mental health condition such as schizophrenia, experts have long theorized that one particular chemical imbalance may be responsible for some symptoms — the dopamine hypothesis of schizophrenia.

But there’s some controversy surrounding this theory. While some earlier research supports this theory, more recent theories focus on imbalances in the neural circuits in the brain rather than imbalances in neurochemicals.

The dopamine hypothesis of schizophrenia states that too much dopamine in the brain — or too little — could directly contribute to symptoms of schizophrenia, particularly those of psychosis such as delusions, hallucinations, and disorganized thinking.

This theory was introduced decades ago due to an observational link between administering dopamine-blocking medications and an improvement of symptoms.

Experts naturally assumed that the medications worked because they reversed an underlying condition of the disorder.

In other words, if blocking dopamine helped, experts felt it meant that there was too much to begin with.

What is dopamine?

Dopamine is a neurotransmitter, a chemical messenger that helps send signals between neurons.

It’s released within specific brain circuits involved with the sensation of pleasure because it’s one of the neurotransmitters directly responsible for motivation and reward.

But dopamine is important for more than just behavior reinforcement and habit formation. It also impacts motor control, cognitive function, and maternal and reproductive behaviors.

It’s widely expressed in the central and peripheral nervous systems.

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The dopamine hypothesis in schizophrenia was based primarily on observational results in its introduction.

Since then, numerous studies pointing at a definite link between dopamine changes and schizophrenia symptoms have backed up the results.

But a few challenges with this theory remain, despite the link being validated through study.

Just as dopamine has been established as an influencing factor, other relevant neurotransmitters have emerged.

A 2018 study summarized the modern dilemma well: Schizophrenia isn’t the only form of psychosis, and dopamine is no longer the only neurotransmitter linked to psychosis.

Study authors note that several interconnected pathways may be involved with symptoms of psychosis. Dopamine is only one of those three, and it may not be the most important or the most influential.

More research is needed to understand the role multiple neurotransmitters play in schizophrenia symptoms.

A 2020 review supports the dopamine hypothesis of schizophrenia based on years of testing and diagnostic imaging.

Unlike the original theory that focused primarily on excess dopamine and dopamine alone, the revised hypothesis makes room for other factors.

A 2014 review, for example, noted the importance of inclusion of other influences in the pathology of schizophrenia, such as glutamate, GABA, acetylcholine, and serotonin alterations.

Experts have long witnessed an association between schizophrenia symptoms and dopamine changes in the body for many years, according to a 2014 study.

But the neurobiological framework for this relationship isn’t well understood.

On the basic level, too much dopamine in particular areas of the brain may contribute to positive symptoms of schizophrenia. Too little dopamine in other regions may result in negative symptoms.

This hypothesis has been challenged over the past 10 years, according to a 2017 review.

Positive symptoms vs. negative symptoms

Positive symptoms in schizophrenia are features that are added, such as hallucinations or delusions.

Negative symptoms indicate a loss in function, such as communication deficits or anhedonia.

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For example, a 2018 study suggested that hallucinations, a well-known positive symptom of schizophrenia, may result from the complex interaction between excess dopamine in the striatal area of the brain and the processing of sensory perception.

In short, dopamine signaling issues may increase the chances your brain will “fill in the gaps” with its expectations rather than reality.

As for negative symptoms, a 2020 study suggests that low levels of dopamine or a dysfunction of dopamine receptors can mean areas of the brain responsible for motivation and reward aren’t being adequately stimulated.

While this accounts for particular negative symptoms such as blunted affect and alogia, more research is needed to understand the link between dopamine pathways and other negative symptoms.

A study from 2021 suggests that the relationship between dopamine and schizophrenia symptoms goes even deeper, particularly concerning the ability to think.

For a long time, experts in the field were unable to explain why someone living with schizophrenia could experience challenges retaining information from rewarding events while at the same time overlearning irrelevant information.

Study authors hypothesized that dopamine dysfunction might strengthen some forms of learning while inhibiting others.

Research only suggests a link between dopamine levels and the manifestation of schizophrenia symptoms.

While the exact cause of schizophrenia is unknown, it’s considered highly heritable, according to a 2017 study.

So having a close relative who lives with schizophrenia might increase your chances of developing this mental health condition.

According to a 2017 study, many genes have been linked to schizophrenia, suggesting that this is a complex disorder with multiple layers of contributing factors.

Schizophrenia is a mental health condition characterized by positive and negative symptoms.

These symptoms may be partially explained by what’s known as the dopamine hypothesis in schizophrenia.

The theory suggests that excess dopamine contributes to positive symptoms such as psychosis, while low dopamine may be responsible for negative symptoms like alogia.

Research supports the theory that dopamine plays an important role in schizophrenia symptoms. But as more information emerges, other neurotransmitters may have similarly critical roles.

Schizophrenia can be an impairing, overwhelming condition. Symptoms of psychosis may place you in situations that can compromise your safety or the safety of others.

If you’d like to learn more about schizophrenia, are interested in more schizophrenia resources, or speak with a trained mental health representative, you can do so at any time by calling the SAMHSA National Helpline at 800-662-4357.