Seasonal affective disorder (SAD) is a subtype of major depressive disorder. It is a multifactorial disorder characterised by the seasonal appearance of its symptoms such as depressed mood, hypersomnia or insomnia, increased or reduced appetite... There are two types of seasonal affective disorder, based on the season when the symptoms appear – summer and winter type. The cause of the disorder has not yet been found, but there are a couple of hypotheses that suggest the possible origin of the disorder. They are called the photoperiodic and phase shift hypotheses, also known as the chronobiological hypotheses. Aside from them, the serotonin and melatonin disbalance may also contribute to the disorder. The goal of this thesis was to discover various treatment options for seasonal affective disorder. Well-known and used treatments are light therapy, cognitive behavioural therapy and pharmacotherapy. No treatment is significantly superior to the others, at least not in all aspects. Light therapy gives the fastest results, but cognitive behavioural therapy shows greater potential to lower the chances of relapse in the next season. Pharmacotherapy is mostly used as a combination treatment with either of the other two. Right now only two drugs have been found to work almost as effectively as light therapy – fluoxetine and bupropion, but they also have side effects. Two other treatments are dawn simulation and negative air ion therapy. Their effect is a little weaker but are still used in patients with milder symptoms. Because all mental illnesses are very hard to treat universally, medical doctors prescribe a combinatorial treatment consisting of more therapies to treat the symptoms in the best possible way for each patient individually.