Up to 40% of people with schizophrenia have a depressive disorder.

The relationship between schizophrenia and depression is a complex one.

Most people with schizophrenia experience at least one depressive episode. In fact, depression often occurs before the first symptoms of psychosis even appear.

However, symptoms of depression and psychosis can occur together in various scenarios. Determining a correct diagnosis can be difficult — even for clinicians.

Schizophrenia and depression are complex mental health disorders that can often occur together. Research from 2020 shows that depression is the third most common condition among people with schizophrenia.

If you have symptoms of both depression and psychosis, it could be a few things:

  • It may be schizophrenia with depressive symptoms or episodes. Up to 80% of people with schizophrenia are estimated to have at least one depressive episode in the early phase of the disorder.
  • It may be schizophrenia and a co-occurring depressive disorder. Up to 40% of people with schizophrenia have a co-occurring depressive disorder.
  • The negative symptoms of schizophrenia can look and feel like depressive symptoms. It may be very hard to distinguish negative symptoms from depressive symptoms — if they’re much different. Some experts suggest that depressive symptoms should be included in schizophrenia criteria.
  • It may be schizoaffective disorder. People with persistent symptoms of schizophrenia and a mood disorder may be diagnosed with schizoaffective disorder.
  • It may be psychotic depression. People with major depression can develop psychotic symptoms, which can sometimes look like the positive symptoms of schizophrenia.

Of note:

It’s important to distinguish schizophrenia from psychosis. Psychosis is a primary feature of schizophrenia, but it can occur in other disorders too.

Here’s a look at schizophrenia and depression individually.

Schizophrenia is a complex mental disorder that impairs a person’s feelings, thoughts, and perception of reality.

Schizophrenia symptoms may fall into three categories:

  • Positive symptoms. These involve symptoms of psychosis, such as hallucinations and delusions.
  • Negative symptoms. These symptoms “take away” from the person’s nature. They may include a lack of motivation, little to no emotional expression, or an inability to feel pleasure.
  • Cognitive symptoms. These symptoms cause difficulties with concentration, memory, and attention. These symptoms often lead to significant disability.

The following factors may make a person more likely to develop schizophrenia:

  • Genetics/family history of mental illness.
  • Family environment.
  • Childhood trauma, including:
    • emotional, sexual or physical abuse
    • neglect
    • poverty
    • bullying
    • insecure attachment
    • loss of a parent
    • witnessing domestic violence
  • Maternal or fetal malnutrition or infection
  • Maternal smoking
  • Having an older father. The chances are three times greater for those with fathers over 55.
  • Being born in the winter or spring. (may be linked to vitamin D deficiency).

Major depressive disorder (MDD) is a mental health condition characterized by a persistently low mood and loss of interest in daily activities.

A MDD diagnosis requires five of the following symptoms for at least 2 weeks (one symptom needs to be “depressed mood” or “anhedonia”):

  • depressed mood
  • anhedonia (loss of interest in previously enjoyed activities)
  • fatigue or low energy
  • poor decision-making
  • sleep problems
  • poor concentration
  • appetite changes
  • restlessness, fast-talking, pacing (psychomotor agitation)

Several factors can make depression more likely:

  • chronic stress
  • faulty mood regulation in the brain
  • history of trauma
  • substance use (including medication)
  • poor nutrition
  • unresolved grief or loss
  • being born female
  • personality traits
  • genetics and family history of mental illness

A note on genetic predispositions

Your genes play a role in whether you will develop some mental or physical health conditions, but they’re only one piece of the puzzle.

Epigenetics is the study of how the DNA you inherit does or does not manifest in you. This means that any genetic predispositions that run in your family can stay inactive or can even be reversible when signs show up early.

There are several reasons why people with schizophrenia feel depressed.

First, certain negative or cognitive symptoms of schizophrenia may mimic or overlap with depressive symptoms.

These include the following:

  • inability to feel pleasure (anhedonia)
  • absence of willpower or inability to act decisively (abulia)
  • lack of speech and verbal fluency (alogia)
  • lack of motivation (avolition)
  • social withdrawal

Sometimes depressive symptoms in schizophrenia can be the result of other factors. For instance, depression can be a side effect of antipsychotic medications, substance use, or the reaction to the consequences of the disorder.

Another possibility is that a person has schizoaffective disorder.

What is schizoaffective disorder?

A person with persistent symptoms of both schizophrenia and a mood disorder may be diagnosed with schizoaffective disorder.

There are two major types of schizoaffective disorder: bipolar type and depressive type.

A diagnosis of schizoaffective disorder is given when a person meets the following criteria:

  • A period in which a major mood episode — either depression or mania — occurs simultaneously with symptoms of schizophrenia.
  • Delusions or hallucinations for 2 or more weeks in the absence of a major mood episode.
  • Symptoms of a major mood episode are present for the majority of the total duration of the illness.
  • Drug use and medications are ruled out as possible triggers.

It’s important to note that the link between psychosis and mood disorder symptoms has been a controversial issue in psychiatry for many years. For instance, schizoaffective disorder is a highly unreliable diagnosis, which has led some experts to question why it’s a separate disorder.

Depression doesn’t cause schizophrenia. However, some people with severe clinical depression will experience symptoms of psychosis, such as hallucinations, delusions and disordered thinking and speech.

These symptoms represent a subtype of depression called “psychotic depression” or “depression with psychotic features.” This condition is also linked to more severe depressive symptoms.

In addition, people with depression can have a greater chance of developing psychosis. And depression is commonly seen in people at high risk for schizophrenia before any symptoms of psychosis occur.

The underlying mechanism between depression and schizophrenia is largely unknown.

However, some 2020 research points to the corticolimbic system, which includes the prefrontal cortices, amygdala, and hippocampus. Other studies suggest the role of brain inflammation in both conditions.

In addition, there is increasing evidence that schizophrenia and depression share certain genetic risk factors.

For instance, a genome-wide association study (GWAS) found similar genetic variations among five major psychiatric disorders:

  • schizophrenia
  • depression
  • bipolar disorder
  • attention deficit hyperactivity disorder (ADHD)
  • autism spectrum disorders

Depression — together with the negative and cognitive symptoms of schizophrenia — can significantly decrease one’s quality of life as well as the disease prognosis. Depression also increases the risk for suicide and substance misuse.

Research from 2020 shows that certain atypical antipsychotics are better than typical antipsychotics in reducing depressive symptoms in schizophrenia:

When antipsychotics aren’t able to manage depressive symptoms well enough, some clinicians may recommend antidepressants, transcranial magnetic stimulation (TMS), or electroconvulsive therapy in severe cases.

Schizophrenia and depression are commonly seen together.

A large majority of people with schizophrenia experience at least one episode of depression. And some people with depression develop psychotic symptoms.

Overall, schizophrenia and depression share several symptoms and genetic risk factors, suggesting they may share a common underlying mechanism.

Both are treatable with medication and therapeutic approaches.