It can be hard to pinpoint the specific cause of a sleep disorder. In some cases, the sleep disorder is actually a symptom of another health problem you are having, such as diabetes or hypothyroidism. Such sleep disorders tend to resolve themselves once the underlying medical condition is treated. On the other hand, chronic sleep disorders may be caused by a combination of stress, mental health issues, ageing, lifestyle or environmental factors. These include: Poor sleep hygiene habits , such as napping in the day or watching TV before sleep An irregular schedule that disrupts your circadian rhythm and sleep-wake cycle, such as working night shifts Mental illnesses , such as depression and anxiety Certain medicines , such as heart medication and antidepressants Caffeine and alcohol consumption Genetics , especially for narcolepsy Ageing