But a new analysis of 11 major mental disorders provides new insights into why comorbidities are common, rather than the exception when it comes to mental illness. The study, published this week in the journal
, found that although not all of them have the underlying gene or set of genes, there are subgroups of disorders including bipolar disorder and schizophrenia; anorexia nervosa and manic-compulsive disorder; and major depression and anxiety share a common genetic makeup.
“Our findings confirm that high comorbidity across some disorders in part reflects overlapping pathways of genetic risk,” said lead author Andrew Grotzinger, an assistant professor in the Department of Psychology and Neuroscience.
He also said this finding about mental health could ultimately open the door to treatments that address multiple psychiatric disorders at once and help to reshape the way diagnoses are given.
“If you had a cold, you wouldn’t want to be diagnosed with coughing disorder, sneezing disorder and aching joints disorder,” Grotzinger said. “This study is a stepping stone toward creating a diagnostic manual that better maps on to what is actually happening biologically.”
Genetic Patterns Lookup
For the study, Grotzinger and colleagues at the University of Texas at Austin, Vrije Universiteit Amsterdam and other collaborators analyzed data from the generally available genome-wide association (GWAS) from hundreds of thousands of people who submitted genetic material to large-scale databases, such as UK Biobank and the Psychiatric Genomics Consortium.
They have been diagnosed with 11 disorders of mental illness, including schizophrenia, bipolar disorder, major depressive disorder, anxiety disorder, anorexia nervosa, depression-compulsive disorder, Tourette’s syndrome, post-traumatic stress disorder, problematic alcohol use, ADHD and autism.
In addition, they analyzed data collected by wearable motion tracking devices and documented physical and behavioral characteristics.
They then used novel statistical genetic methods to identify common patterns throughout the psychiatric disorder.
They found that 70% of the genetic signal associated with schizophrenia was associated with bipolar disorder. That finding was surprising, since under current diagnostic guidelines, physicians would not normally diagnose a person with both.
They found that anorexia nervosa and manic-compulsive disorder have a strong, shared genetic makeup, and that people with a small body type or low BMI (body mass index) have a genetic predisposition to these disorders.
Since the two diagnoses often go together, it is not surprising that the study found that there is a large genetic correlation between anxiety disorder and major depressive disorder.
While analyzing the accelerometer data, the researchers found that the disorders that cluster together share genes that affect how and when we move around during the day.
For example, people with internalizing disorders, such as anxiety and depression, have a genetic makeup associated with reduced mobility throughout the day. Compulsive disorders (OCD, anorexia) tend to be associated with genes associated with increased movement throughout the day, and psychiatric disorders (schizophrenia and bipolar disorder) are genetically linked to excessive movement in the early morning.
“When you think about it, it makes sense,” said Grotzinger, noting that depressed individuals often present as fatigued or low energy while those with compulsive disorders can have difficulty sitting still.
Therapy for Multiple Disorders
In total, the study identifies 152 genetic variants shared across multiple disorders, including those already known to affect certain types of brain cells.
For example, genetic variants that affect excitatory and GABAergic brain neurons involved in important signaling pathways in the brain appear to be strongly related to the genetic signal shared in schizophrenia and bipolar disorder.
While much remains to be done to determine exactly what the identified genes are doing, Grotzinger sees this research as the first step in developing therapies that can alleviate many disorders through a single treatment.
“People are more likely today to be prescribed multiple medications intended to treat multiple diagnoses and in some instances those medicines can have side effects,” he said. “By identifying what is shared across these issues, we can hopefully come up with ways to target them in a different way that doesn’t require four separate pills or four separate psychotherapy interventions.”
Meantime, people can now understand the genetics underlying their psychiatric disorders and may provide comfort to some patients with mental illness.
“It’s important for people to know that they didn’t just get a terrible roll of the dice in life – that they are not facing multiple different issues but rather one set of risk factors bleeding into them all.”
Source: Medindia
