Prolonged fear about a particular object or situation can eventually lead to a phobia of that object or situation. Bad experiences, such as getting bitten by a spider, can cause phobias, or they can seem to develop without cause, like a fear of birds even when one has never been harmed by one. Phobias can quickly expand, leaving an individual afraid of not just of the type of spider that bit them, but of all spiders, or even of insects in general.

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