Depression affects one in 10 American adults, and although therapeutic drugs are available, their response rates are often slow as it is difficult to get individualized treatments. Lots of research has occurred in the past decades regarding the chemical and genetic factors that cause imbalances in the brain that lead to depression. Now, a new study suggests that depressed individuals don't have the proper amount of a small molecule found in the brains of other humans. Finding out ways to boost levels of this molecule may be the key to curing depression, according to a new study.

Depression is a mental disorder characterized by a state of low mood, sadness, loss of interest and pleasure with certain activities, and feelings of guilt. There are different forms of depression. In its most severe form, depression may cause patients to develop suicidal tendencies, although many antidepressant medications, like Prozac and Zoloft, are available and have proven to be successful in several cases. What works for one patient, however, may not work for the other, so physicians use their own judgement when prescribing medications.

With the discovery of this new molecule, called miR-1202, doctors may be able to identify the exact line of treatment depending on the levels of the molecule in the patient. A paper on the discovery, published in the journal Nature Medicine, was written by Dr. Gustavo Turecki, a professor in the Department of Psychiatry at McGill University, and his team.

"Using samples from the Douglas Bell-Canada Brain Bank, we examined brain tissues from individuals who were depressed and compared them with brain tissues from psychiatrically healthy individuals," Turecki said in a press release. "We identified this molecule, a microRNA known as miR-1202, only found in humans and primates and discovered that it regulates an important receptor of the neurotransmitter glutamate".

Glutamate is known to be present in high levels in the brain and is an important regulatory protein in several neural processes. An imbalance in its levels can cause depression and other conditions like obsessive-compulsive disorder (OCD).

The team conducted experiments on patients diagnosed as clinically depressed and used antidepressants that changed the levels of microRNA in these individuals.

"In our clinical trials with living depressed individuals treated with citalopram, a commonly prescribed antidepressant, we found lower levels in depressed individuals compared to the non-depressed individuals before treatment. Clearly, microRNA miR-1202 increased as the treatment worked and individuals no longer felt depressed," Turecki said. "Although antidepressants are clearly effective, there is variability in how individuals respond to antidepressant treatment. We found that miR-1202 is different in individuals with depression and particularly, among those patients who eventually will respond to antidepressant treatment."

The discovery will greatly streamline how and which antidepressants need to be used, according to Turecki, and will lead to “development of new and more effective antidepressant treatments."

Source: Turecki G, et al. Nature Medicine. 2014.