Prince Harry has made a personal plea for military personnel with mental health issues to try to talk about their problems.
The 32-year-old, who served as an Army officer for 10 years and was twice deployed to Afghanistan, said: "It is incredibly difficult to talk about mental health in the armed forces. It is still a very difficult conversation.
"As a military person, once you put that uniform on during your training, you are taught to be invincible and not to let anybody down.
"However, a lot of individuals prefer turning to alcohol rather than a friend."
Harry was taking part in a Veterans' Mental Health Conference in central London, where he told the 210-strong audience that mental health issues are "not a life sentence".
He attended as part of the Heads Together mental health campaign which he leads with the Duke and Duchess of Cambridge.
The gathering included former military personnel like himself, academics, and representatives from the NHS, the Ministry of Defence and mental health organisations.
The Prince chaired a discussion involving veterans about the help which can be triggered by powering through the stigma linked to mental health problems and having an open conversation about it.
The event was organised by the King's Centre for Military Health Research with the Forces In Mind Trust.
Backers of the conference include Contact, the military community mental health coalition which works with veterans, service personnel and their families to find the right help for issues such as anxiety and depression.
Contact is the military-focused arm of the Heads Together campaign.
Harry said his "main fear" was that people will not get the appropriate help due to the "stigma" surrounding the situation.
Stressing that mental fitness is just as important as physical fitness, he said: "I am saying at this time to all the military people in this room and beyond - it is OK to have depression, it is OK to have anxiety and it is OK to have an adjustment disorder.
"We need to improve the conversation. We all have mental health in the same way we all have physical health."