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You don't have to be depressed to be goth... you just have to ask yourself this do you like or are drawn to the darker side of things, aspects of life or gothic music? Are your friends goth... do you get along with other people or find yourself attracted to other people or things generally referred to as 'gothic', or no? It can make a world of difference if you think you're becoming 'goth' or are just feeling gloomy but will get over it with time.

If you can't tell then just give it some time and your prefereces will tell you eventually, it could just be a faze or maybe you're just really depressed, wear black if you want (if you do), but that alone wont make you Goth.

Some gothic people are actually very happy people, happy with being Goth.

Also a little more information would help.