Four genes associated with OCD identified

By Dr. Ananya Mandal, MDOct 18 2017

There are found genes that have been identified to be associated with obsessive compulsive disorder (OCD). These genes have been found to alter the circuitry of the brain in a manner that could lead to OCD. These genetic links also point to the fact why OCD sometimes runs in families. The study is published in the latest issue of Nature Communications.

OCD usually affects personal, social and familial lives of the sufferer causing intense anxiety. This team of researchers led by Hyun Ji Noh at the Broad Institute of MIT and Harvard and her colleagues, compared 608 genes in 592 persons who had OCD and 560 persons who did not have OCD.

Image Credit: Pathdoc / Shutterstock

These specific genes were chosen on the basis of several studies that had shown previously that they could be associated with OCD. Of these 608 candidate genes that were tested, 222 had been shown to be present in laboratory mice who groomed compulsively (a symptom akin to human OCD). A further 196 genes tested were found among autistic individuals who showed repetitive behaviors to relieve anxiety.

Another 56 genes were identified from a study on dog compulsive behaviors where the canines indulged in repetitive behaviors such as chasing their tails or pacing back and forth etc. They used hybrid capture arrays and pooled sequencing on the Illumina GAII or HiSeq 2000 to profile 13.2 million bases of coding among the participants.

The final results of the study showed that there were four different genes in people with OCD that were distinctly absent among those who did not have OCD. These are active in a brain circuit that connects three major regions of the brain namely – thalamus, cortex and striatum.

Here the striatum has areas that help one learn and their messages are relayed via the thalamus to the cortex from where the decisions are made. Among people with OCD, this loop becomes dysfunctional.

The genes identified include HTR2A – which is also involved in a chemical regulation of the brain called serotonin.

Serotonin derangements are the cause for several psychiatric disorders including depression. Noh explained that this could be the reason why people with OCD have problems with maintaining normal levels of serotonin in their brain.

Correction of serotonin levels using SSRIs (antidepressant drugs) thus can benefit persons with OCD, she explained. Alterations of the genetic pathways could be a future approach to treating this condition she added. Four genes identified to be significantly associated with OCD include NRXN1 and HTR2A genes and the CTTNBP2 and REEP3 genes.

The team after obtaining these results compared them in a further 729 cases of OCD and 1105 normal persons too. They then compared it with 33,370 controls that did not have OCD.

OCD

OCD is one of the commonest psychiatric conditions. Over 3.3 million people suffer from this condition in the US and 750,000 are diagnosed with this disease in the UK.

Characteristics of OCD include an abnormal need for order and an inability to be flexible over how a particular thing should be done.

Patients have a strict preference for laws, rules and regulations and have an inability and unwillingness to relinquish responsibilities to others.

Symptoms of OCPD that help in diagnosis:

• Fixation with rules and details and adherence to ethical and moral codes
• Fixation with lists
• Perfectionism to the point it interferes with completing tasks
• Excessive preoccupation with work to the point of ignoring personal, social and familial needs
• Excessive hoarding
• Excessive caprice, miserliness and frugality
• Strained relationships with spouse, family and co-workers

Diagnosis of OCD is made when a person is demonstrating a number of the above symptoms which may be leading to impaired familial, occupational, social or emotional relationships. For OCD to be diagnosed, not all of the symptoms described need to be present in an individual.

Source: https://www.nature.com/articles/s41467-017-00831-x