Spending time online is normal behavior for teenagers. But too much Internet use by teens -- or too little, for that matter -- might be related to depression, a new study finds.

The findings, reported in the journal of Pediatrics, do not mean that the Internet is to blame. For one, teens in the study who spent no time online were also at increased risk of depression symptoms.

Instead, the researchers say that both heavy Internet use, and non-use, could serve as signals that a teenager is having a hard time.

For the study, Dr. Pierre-Andre Michaud and colleagues at the University of Lausanne, Switzerland, surveyed 7,200 individuals ages 16 to 20 about their Internet use.

Those who were online more than two hours per day were considered "heavy" Internet users, while those online anywhere from several times per week to two hours per day were considered "regular" users.

The teenagers also answered a number of health-related questions, including some standard questions about "depressive tendencies" that gauge how often a person feels sad or hopeless.

Compared with regular Internet users, the study found, kids who were heavy users or non-users were more likely to be depressed or very depressed.

Among male teens, heavy users and non-users were both around one-third more likely to have a high depression score, compared to "regular" users. Among girls, heavy Internet users had an 86 percent greater chance of depression, while non-users had a 46 percent greater likelihood compared to regular users.

That was with factors like family income and any chronic health problems taken into account.

However, the average depression scores among non-users, regular users and heavy users alike were all toward the lower end -- between 1 and 2 on a scale of 1 to 4, with 1 being "not depressed at all."

Since teenagers typically go online to connect with friends, the researchers speculate that those who are never online may be more socially isolated.

(Read by Nelly Min. Nelly Min is a journalist at the China Daily Website.)

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(Agencies)