Cologne, Germany - Teenagers commonly experience mood swings and are not always approachable, and this behaviour can make it hard for parents to differentiate such emotional fluctuations from genuine depression.

Experts say it's important for parents to monitor their teenager's moods and seek treatment when warranted.

"Parents should make an appointment with a paediatrician, if their teenager falls into a deep depression or if there is a distinct change in the teenager's behaviour that lasts more than two weeks," said Ulrich Fegeler of Germany's association of paediatricians in Cologne.

A medical examination can rule out other diseases such as under active thyroid and help with the search for a psychiatric counsellor. As in adults, some teenagers who are depressed are also more prone to suicide.

A depressed teenager can experience restlessness, anxiety, difficulty concentrating and a defiant attitude, changing from one to the other. They commonly have problems achieving, withdraw into themselves, suffer a lack of drive, fear the future and have problems with self esteem.

"Irritability, a low tolerance for frustrations and a quick temper also can indicate depression in puberty," said Fegeler.

Statistically, the incidence of psychological diseases increases greatly from age 12. Painful experiences such as a break-up and loss, as well as certain parenting styles and hereditary factors, can trigger depression.

An estimated one in 10 teenagers suffers a depressive phase at least once before reaching adulthood. As in the adult population, females are two to three times more likely than males to be affected. (dpa)