Though it has become widely publicized in the U.S. due to awareness campaigns, depression remains a serious problem for those who experience its debilitating symptoms. More people are seeking treatment, but they may not see immediate improvement. Antidepressants typically require approximately two weeks to begin making an impact on the patient. However, in many cases, the medication may not be effective, or patients may discover that the unpleasant side effects are not outweighed by any benefit of taking the drug. A patient may endure multiple rounds of medication trials before one is determined to be a good match. Medication is typically paired with therapy to help a patient learn to navigate a persisting low mood associated with depression. While therapy, exercise and a healthy diet are all components of treating depression, medication can be an important part of recovering a high quality of life. A study conducted by Montreal-based researchers at McGill University and the Douglas Institute provides new evidence about the way depression impacts individuals at the molecular level. Among depression patients, there is a lower level of a molecule that is found only in humans and other primates. The findings may be critical in developing new treatments for depression. The study, published in a recent issue of the journal Nature Medicine, found that a molecule called miR-1202 may provide a reliable marker for depression. Manipulation of the molecule with medication may lead to more effective treatment. In addition, the detection of the molecule level may help identify patients who could respond well to medication. The study was led by Dr. Gustavo Turecki, a psychiatrist at the Douglas Institute and professor in the Faculty of Medicine at McGill. The researchers accessed samples through the Douglas Bell-Canada Brain Bank and studied the tissues taken from depressed individuals, which they compared with the brain tissues of psychiatrically well individuals. The molecule miR-1202 was identified in primates and humans. It was determined that this marker regulates a critical receptor of glutamate. In their experiments, the team was able to show that antidepressants are effective at changing the levels of the molecule in the depressed individuals. In tests with depression patients, the researchers measured the levels of the molecule in those treated with citalopram. This commonly-prescribed medication in depressed patients worked to increase the molecule in the patients over the course of treatment. Turecki explains that though antidepressants are one of the most common treatments for depression, patients respond in various ways to the medication. In some cases, patients respond well, with few side effects and a positive response in symptoms. For others, however, the drug can prove to be not only ineffective, but carrying with it unpleasant side effects. The researchers found that the molecule was variable among individuals, and that those with the lowest level of the molecule tended to be the most likely to eventually respond to antidepressant treatment. The researchers believe that the findings may provide a new target for the development and testing of new antidepressants that are more effective than those currently available. Treating depression requires a commitment by the patient to finding the right fit for recovery. Therapy in conjunction with medication is often a successful combination, but patients may require a trial-and-error process to find the right medication for their symptoms. Measuring the presence of the molecule may help physicians determine whether medications will have an impact on an individual\u2019s symptoms.