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 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 gauge¹ 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 depressed² 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 chronic³ 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 isolated⁴.

虽然上网对于青少年来说是很正常的行为，但是一项调查发现，上网时间过长或者过短可能会导致抑郁。

这项发表在《儿科学》杂志上的研究并不是说网络该为抑郁症负责，因为在接受调查的人群中，那些不上网的青少年出现抑郁症状的几率也增加了。

事实上，研究人员称青少年上网时间过长和不上网都表明这个孩子过得不好。

在研究中，皮埃尔•安德烈•米肖博士和他在瑞士洛桑大学的同事一起，调查了7200名年龄在16岁到20岁之间的青少年的上网情况。

那些每天上网时间超过两小时的人被视为“过度上网者”，而那些上网时间介于“每周几次”到“每天两小时”的人则被视为“正常上网者”。

这些青少年还回答了一些和健康相关的问题，其中包括一些和“抑郁倾向”有关的常规问题，这些问题可测算出一个人感到忧伤或绝望的频繁程度。

研究发现，跟“正常上网者”相比，过度上网和不上网的孩子更容易感到“抑郁”或“很抑郁”。

就男孩而言，过度上网和不上网的人抑郁分值高的可能性都比正常上网者高约三分之一。而女孩当中过度上网者患抑郁症的可能性比正常上网者高86%，不上网者比正常上网者高46%。

这一研究将家庭收入、慢性病等因素都考虑在内。

不过，不论是不上网者、正常上网者还是过度上网者，他们的平均抑郁分值都较低——都在1到2分之间。抑郁程度有1分到4分四个等级，1分表示“一点都不抑郁”。

一般来说，青少年上网是为了与朋友们联系，因此研究人员推测，那些从来不上网的青少年可能更自闭。