New York, Aug 12 (IANS): The bond between parent and child extends far beyond sharing similar looks or behaviours as a new study suggests that treating depression in teenagers may benefit their parents' mental health too.

The findings suggest that when a teenager's depression improved through treatment, so did the depression experienced by his or her parents.

"Depression is a massive public health concern that will take a variety of approaches to better manage. We believe our study is among the first to evaluate how the emotional health of a child can impact that of the parents," said co-author Mark A. Reinecke from the Northwestern University in the US.

For the study, presented at American Psychological Association's 126th Annual Convention, the research team involved 325 teenagers who had been diagnosed with depression and 325 of their parents or caregivers.

The teenagers were randomly assigned to one of three groups -- those who received cognitive behavioural therapy, those who took anti-depressants or those who used a combination of both.

The first treatment period ran for nearly one year, with an additional year of follow-up visits, the researchers said.

One-quarter of the parents who participated also reported moderate to severe levels of depression before the treatment period, the researcher added.

The treatment process was not family-based, though some portions included the parent.

The researchers found a positive ripple effect because when the severity of a teenagers's depression lessened, so did similar symptoms in the parent, regardless of what treatment was used.

"More young people today are reporting persistent feelings of sadness and hopelessness and suicidal thoughts," said Kelsey R. Howard from the varsity.

"This research may help health care providers as we grapple as a nation with how to address these alarming trends," Howard noted.