Key symptoms are:
- a persistent feeling of sadness and low mood
- loss of interest in the world around you and no longer enjoying things that used to give pleasure
- lack of energy and feeling tired all the time
Other symptoms can include:
- disturbed sleep, such as not being able to fall asleep during the night and then being sleepy during the day
- difficulties with concentration and making decisions
- low self-confidence
- poor appetite or an increase in appetite/"comfort eating"
- feeling very agitated or alternatively very apathetic
More top news
John Cantlie, who worked for a number of Fleet Street newspapers, is thought to have been taken hostage in November 2012.
The union published a 'no show' league table for last year the worst offenders for cancellations.
Zalkalns was jailed in his native Latvia for eight years in 1988 after he admitted killing his wife with a piece of electrical equipment.