Depression is one of the mood disorders and is quite common in the modern population; it is estimated that 15% of people have experienced the symptoms of the disease. Patients with clinical depression experience sadness, despair, or a tendency to cry and a loss of hope for the future for most of the day. In some people there is also a decrease in interest or pleasure in most of the activities that previously interested or gave pleasure, a feeling of continuous tiredness and demotivation. These symptoms may be accompanied by physiological signs such as impaired appetite, sleep disturbances, reduced ability to concentrate, memory and attention. Depression is a multifactorial disorder, which means that various aspects contribute to the onset of the disease. According to the bio-psycho-social model they can be: biological (genetic, hormonal, related to the use of drugs or somatic diseases), psychological (traumatic situations in childhood, difficulties in the psychophysical developmental stages, exposure to stress of significant importance), or socio-familial (family conflicts, traumatic bereavements and separations, particularly stressful working contexts, “mobbing”). Depression can be prevented and treated: adequate knowledge of depressive disorder can help to recognise the distinctive signs and motivate people to seek help. Therapeutic approaches are varied and must undoubtedly be personalised: in some cases psychological support plays an important role in modifying negative styles of thought and behaviour, in other cases pharmacological support and assessment of the socio-environmental context are just as indispensable.