Jyoti Kinghorn 
Schizophrenia and bipolar disorder are considered to be distinct mental disorders. However, they have some overlapping symptoms that can sometimes make diagnosis difficult. Research shows that there is also considerable overlap in the genes, brain metabolites, and internal brain structure of people who suffer from these conditions. Some researchers have suggested that these conditions should be viewed as a continuum or a spectrum of psychotic spectrum disorders instead of discrete ailments.
How schizophrenia is diagnosed
Schizophrenia is characterized by losing one’s connection with reality, and has the following diagnostic symptoms:
- Hallucinations or delusions.
- Disorganized speech, disorganized or erratic movements.
- Negative symptoms such as a lack of facial expressions.
To be diagnosed with schizophrenia, a patient must have at least two of these symptoms. The symptoms must have lasted at least a month in duration (or most of the time during that month). Hallucinations and delusions are required symptoms, and the patient must have at least one of these for a schizophrenia diagnosis.
How bipolar disorder is diagnosed
Bipolar disorder is characterized by extreme mood swings composed of manic and depressive episodes.
The manic episode is an emotional high where the person feels extremely happy or overjoyed, is full of energy, talks very fast, doesn’t sleep enough, makes lots of plans but gets distracted easily, feels indestructible, and does things out of character which can put them in danger. The person may suffer from hallucinations or delusions.
The depressive episode is characterized by feeling pessimistic, sad, lacking energy, feeling empty or worthless, and having suicidal thoughts.
The manic and depressive episodes may cycle rapidly or slowly or may be present at the same time.
Bipolar I is diagnosed when the patient has had at least one manic episode which may or may not have psychosis (losing touch with reality).
Bipolar II is diagnosed when there is at least one hypomanic episode (less severe but present symptoms of a manic episode), and at least one depressive episode.
A patient may have both Bipolar I and II, which could significantly affect their social and occupational functioning
The association between schizophrenia and bipolar disorder
While the conditions are considered clinically distinct, there are many areas of considerable overlap between schizophrenia and bipolar disorder.
1. Overlapping symptoms
Patients with schizophrenia experience psychosis where they lose touch with reality. They can have hallucinations where they see, hear, smell, or feel things that are not there. They can also have delusions where they make up their minds about something being true, and do not let reality change their mind. For example, some patients may believe that someone is controlling them or wants to hurt them, or that someone is sending them secret messages through TV or radio shows.
Patients with bipolar disorder who are going through manic episodes can also have psychosis, where they feel so indestructible that they may believe that they are made of metal, or that they are the president of the U.S.
The overlap can be so stark in some cases that a clear-cut diagnosis may be difficult. In 1933, Kasanin coined the term “schizoaffective disorder” to describe the condition when individuals show symptoms of both schizophrenia and bipolar disorder- they have hallucinations or delusions with manic and depressive mood swings.
2. Overlapping genes
While we don’t fully understand why someone gets schizophrenia or bipolar disorder, genetics play a big part.
Studies with twins seem to indicate that genetics may account for about 73% of the tendency of a person to develop bipolar disorder, with the environment being responsible for the rest.
Schizophrenia is heritable too. The risk in the general population for a person to develop schizophrenia is about 1%. But if both parents have it, the risk can be 50%, and if an identical twin has schizophrenia, the risk is between 40-65%.
Scientists have identified genes that are linked to schizophrenia and bipolar disorder, and some of them are the same. For example, the gene AKAP11 is a strong risk factor for both schizophrenia and bipolar disorder.
3. Reduction in neurometabolites
Some metabolites such as N-acetylaspartate (NAA) only occur in the brain. Using a non-invasive technique called proton magnetic resonance spectroscopy, scientists have observed that NAA levels are lower in both schizophrenia and bipolar disorder.
4. Internal structure of the brain
Both schizophrenia and biopolar disorder show changes in the brain’s physical internal structure (morphology). In both disorders, there is a reduction in grey matter (primarily in the bilateral insula and anterior cingulate cortex). In both disorders, there is atrophy in the brain areas associated with cognitive function- the hippocampus, amygdala, and the thalamus. However, the changes are much more subtle in bipolar disorder, and much more prominent in schizophrenia.
Diagnosis and treatment
Based on the patient’s family history and symptoms, the psychiatrist may diagnose the disease as one disorder, or a combination. Many of the treatment strategies and drugs can also be the same. A part of the doctor’s diagnosis is based on self-evaluations, so it is important to be diligent and honest in documenting your or your loved one’s symptoms. Many people with schizophrenia and bipolar disorder can function and take care of themselves with medication, so it is important to seek medical treatment.
The treatment of mental disorders is for a lifetime. However, based on changing symptoms or drug effects/ side effects, treatment regimens may need to be changed. Therefore, keeping an open communication channel with your doctor is beneficial. Never stop your medication without consulting with your doctor first.
Moving beyond diagnoses
Researchers are constantly searching for new treatments that can help patients with mental disorders. But fitting patients into strict diagnostic categories of one mental disease or other can be problematic because symptoms and conditions often overlap in people. Therefore, to support research on mental health, the National Institute of Mental Health (NIMH) has introduced the RDoC framework to help study “mental health and illness in terms of varying degrees of dysfunction in fundamental psychological/biological systems”. This system can help researchers develop treatments based on a comprehensive view of a patient’s health not necessarily fitting them in categories of diagnosed diseases.
The information provided in our blog posts is for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this blog.
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