Depression is a state of low mood and aversion to activity.  Depressive disorder is a medical term that refers to a mental and behavior disorder ,. It affects the person’s thinking, mood, motivation, feelings and overall well-being.  Anhedonia is the main symptom of depression. This refers to a loss or loss of enjoyment in activities that are usually a source of joy for people.  Depression is a sign of mood disorders like major depressive disorder and dysthymia . It is a temporary reaction to life events such as the death of a loved. You may experience sadness, difficulty thinking and concentration, and an increase or decrease of appetite or time spent sleeping. Depression can cause feelings of hopelessness, dejection and even suicidal thoughts. This can be either short-term or long-term. Depression in adulthood can be caused by childhood traumas such as neglect, bereavement or physical abuse.  The likelihood of suffering from depression in adulthood is significantly affected by childhood sexual or physical abuse. 
Changes in life that can influence moods and depressive moods include, but are not limited to, childbirth, menopause financial difficulties, unemployment, stress (such a from work, education, living conditions, etc. ), a diagnosis of cancer, HIV, or other medical condition. Bullying, the death of a loved-one, natural disasters (cancer, HIV, etc. ), social isolation, rape and relationship troubles, jealousy or separation, or a catastrophic injury.  Adolescents may be especially prone to experiencing a depressed mood following social rejection, peer pressure, or bullying. 
Globally, more than 264 million people of all ages suffer from depression.  The global pandemic of COVID-19 has negatively impacted upon many individuals’ mental health, causing levels of depression to surge, reaching devastating heights. A study conducted by the University of Surrey in Autumn 2019 and May/June 2020 looked into the impact of COVID-19 upon young peoples mental health. The Journal of Psychiatry Research Report published this study.  The study showed a significant rise in depression symptoms and a reduction in overall wellbeing during lockdown (May/June 2020) compared to the previous Autumn (2019). Levels of clinical depression in those surveyed in the study were found to have more than doubled, rising from 14.9 per cent in Autumn 2019 to 34.7 per cent in May/June 2020.  The study also highlights the association between certain life events and developing depression.