Bipolar disorder is a mental condition characterized by extreme mood swings that affect mood, thinking, behavior and the ability to perform activities of daily living. It affects for months or years, in stages, where calm and normal behavior is interspersed with manic and depressive episodes. According to WHO, it affects 45 million people worldwide, being the sixth leading cause of disability in the world.
The cause is of biological and genetic origin. The limbic system is responsible for regulating emotions and maintaining a stable mood according to the circumstances. In people affected with bipolar disorder, the limbic system does not function properly, so that their mood changes abruptly for no apparent reason.
In addition, there are a number of risk factors that can help to trigger the disease:
- Family history. Bipolar disorder has a strong genetic basis, increasing the risk significantly if there are direct relatives affected.
- Consumption of drugs such as cannabis or cocaine.
- Certain drugs, such as corticoids can trigger episodes in susceptible people.
- Childbirth and postpartum. In some women they can act as triggers. In addition, women who are susceptible to or diagnosed with bipolar disorder are more prone to postpartum depression.
- Medication withdrawal. This is the main risk factor and cause of relapse in people diagnosed with bipolar disorder.
Despite its complex etiology, bipolar disorder has a high hereditary component, with genetic factors accounting for an estimated 80% of the basis of the disease. Genetic genome-wide association studies carried out so far have revealed an important fraction of the genetic etiology of the disease. In a GWAS study carried out in more than 40,000 patients and 40,000 controls, 63 susceptibility loci were found. The risk alleles found were predominantly in genes involved in synaptic signaling pathways, in particular those with specific expression in neurons of the prefrontal cortex and hippocampus. In addition, signal was also found in genes encoding for antipsychotic, antiepileptic and anesthetic drug targets, such as HTR6, MCHR1 or FURIN.
Bipolar disorder is characterized by alternating manic episodes with depressive episodes, of variable duration. Each of the phases is characterized by different aspects, although the manifestations can be very variable from one person to another.
The manic phase is characterized by:
- Abnormal episodes of optimism, nervousness or tension.
- Agitation, increased activity or energy.
- Exaggerated sense of well-being.
- Decreased need for sleep.
- Reckless behaviors and lack of self-control.
The depressive phase, in turn, may include the following symptoms:
- Sadness or low mood.
- Difficulty concentrating.
- Eating problems, poor appetite and weight loss.
- Fatigue and tiredness.
- Feelings of worthlessness or guilt.
- Loss of pleasure in activities once enjoyed.
- Loss of self-esteem.
- Thoughts of death or suicide.
- Difficulty falling asleep or sleeping too much.
- Withdrawal from friends or activities once enjoyed.
Both of these phases can cause obvious difficulties in carrying out daily activities such as work, school, social activities or relationships.
There is no effective way to prevent bipolar disorder. However, early treatment can help prevent the disorder from worsening and can lead to a good quality of life.
If you have been diagnosed with bipolar disorder or have a first-degree relative who is affected, it is important to keep the following in mind:
- Pay attention to the warning signs. Treating symptoms early can help minimize their effects.
- Avoid drugs and alcohol.
- Have a good sleep hygiene.
- Take medication correctly. Abandoning treatment or reducing the dose may help trigger new episodes.
13.5 million variants
Mullins N, Forstner AJ, O'Connell KS, et al. Genome-wide association study of more than 40,000 bipolar disorder cases provides new insights into the underlying biology. Nature Genetics. 2021 Jun;53(6):817-829.