Looking Into Genetic Links: Are Mental Health Issues Hereditary?

If you are experiencing mental health issues, you would naturally want to know its causes. Sometimes, more than one family member has the same mental illness; at other times, only one has it. While the origins of mental health issues remain elusive, recent research has suggested that many conditions may carry a genetic element to them. For example, an international study led by the University of Wollongong, Australia in 2023 found a possible genetic link in patients with disorders such as depression and schizophrenia.

Genetics do not necessarily cause mental illnesses but can be a factor that increases the likelihood or risk factor of having one. Staying up-to-date with the research in the mental health field is essential for practitioners or MSN-PMHNP students, as it is the best way to accomplish professional development and ensure patient well-being. Let’s take a look at what the recent research says about the hereditary factors for some of the most common mental-psychiatric conditions in the U.S. 

Depression

Affecting approximately 350 million people around the world, and about 18.5% of American adults, depression is a serious yet common mental illness. It is largely characterized as a mood disorder, can be either temporary or long-term, and involves symptoms such as constant sadness, agitation, hopelessness, or emptiness. Depression is more than just feeling ‘sad’, and numerous researchers have observed that it runs in families; people who have the disorder may also have another close family member – a relative, a parent, or a sibling – who experiences the same disorder. 

The estimated genetic heritability of major depressive disorder (MDD) rests at around 40%, though the exact genetic composition of depression remains an enigma. There has been a wide range of theories on the origins of depression, from the serotonin transporter gene theory to the neuroplasticity disturbance theory. The former posits that modifications in the SLC6A4 (the serotonin transporter gene), which directly affects our mood and emotions, are linked to depressive mood disorders, as there is a definite correlation between decreased serotonin levels and depressive moods.

Schizophrenia 

As mentioned before, schizophrenia is a disorder with a well-established hereditary genetic influence. Schizophrenia is a serious and complex mental illness that is known for psychosis, being out of touch with reality, hallucinations, and major disturbances in thought, perception, and behavior. While it affects only 1.1% – or 2.8 million – of all adults in the U.S., its heritability risks however reach as high as 79%. 

A worldwide study published in 2014 by the Psychiatric Genomic Consortium uncovered about 80 genes across 108 regions as being linked to schizophrenia. Researchers compared the DNA of over 37,000 individuals who were affected by the disorder and 113,000 who were not. The main conclusion was that a malfunction in a gene called dopamine receptor D2 (DRD2), which is responsible for the secretion, storage, and regulation of dopamine, was a key pattern for those with schizophrenia.

The question of whether it is too much or not enough dopamine that increases the risk of schizophrenia remains up for debate. On one hand, some research suggests that too many dopamine receptors in the mesolimbic pathway, a major dopamine pathway mostly known for its pleasure and reward functions, can cause ‘positive’ schizophrenic symptoms such as delusions and hallucinations. On the other hand, other research says that a lack of dopamine activity in regions such as the prefrontal cortex, which regulates our thoughts, actions, and emotions, can cause ‘negative’ schizophrenic symptoms such as social withdrawal and decreased cognitive function.

Bipolar Disorder

Like schizophrenia, bipolar is another disorder that bears strong heritability. About 4.4% of American adults experience bipolar disorder throughout their lives, while heritability rates reach between 70-90% – though this does not assume that if one family member has the condition, another family member will inevitably also develop it. Things such as environment, life changes, or physical injuries to the brain are other influences to be mindful of. 

Bipolar is characterized by periods of extreme mood swings, usually between depressive lows and manic highs. Bipolar I is the most serious form of the disorder, while bipolar II and cyclothymic disorder are more mild. Symptoms of Bipolar I disorder usually follow the course of rapid cycling, which refers to four or more shifts between different moods within 12 months. 

From the genetics standpoint, researchers have tentatively traced the increased likelihood of developing bipolar disorder as correlative to problems with calcium signaling, which refers to the regulation of calcium secretion, amongst genes such as GACNA1C and ANK3. Other research suggests that the AKAP-11 gene, which interacts with lithium treatments of the disorder, is a high-risk factor. 

Eating Disorders

Traditionally, anorexia and bulimia nervosa are viewed as being influenced by sociocultural factors. About 9%, or 28.8 million, Americans will have an eating disorder in their lifetime, with 8.6% being females and 4.07% being males. Anoxeria involves an abnormal fear of gaining weight and an obsession over what one is eating; bulimia is characterized by sudden binge eating and starving to avoid weight gain. 

In comparison to bulimia, anorexia has a higher genetic factor. If a person is born into a family that has experienced anorexia, they are 11 times more likely to develop the disorder than others. While it is rare for genetic factors to be decisive for bulimia or binge eating disorders, there is still nevertheless a genetic risk factor present, such as the CYFIp2 gene.  

The Verdict

As always, even if a family member has a mental health disorder, it does not mean that others will inherit it too. Likewise, if a mental health disorder does not run in the family, it is still possible for another to develop one. 

Genetic influences should always be placed with environmental factors. For instance, trauma – and especially childhood trauma – can dramatically increase the risk of depression. Some researchers have even proposed that changing the environment can be an effective ‘escape’ from a disorder if one is more predisposed to developing it.