More than a quarter of professional footballers suffer from depression or anxiety problems, according to a new study carried out by the international players' union FIFPro.
The research shows that 26 percent of players reported mental health problems, with that figure rising to 39 per cent among retired players.
FIFPro's study of 180 current players in six countries -- Scotland, the Netherlands, the Republic of Ireland, the U.S., Australia and New Zealand -- showed that seven percent smoke, while 19 percent reported "adverse alcohol behaviour."
FIFPro's chief medical officer Dr Vincent Gouttebarge said: "Contrary to popular belief, the life of a professional footballer has some dark sides.
"Former professional footballers report more mental health problems than current players, endorsing that the period just after retirement from professional football is a critical one for many players.
"We found mental illness among former professional footballers occurs more often than in other measured populations.''
Stan Collymore, Paul Gascoigne, Niall Quinn and Michael Johnson have spoken in the past of their battles against depression, while former Germany goalkeeper Robert Enke committed suicide in 2009 while suffering from depression.
In this latest study, former New Zealand captain Chris Jackson, who played schoolboy football with Wimbledon, said his disappointment at not making it into European football let to depression which set him on a path of drug and alcohol abuse.
Jackson, 43, who now works as a cleaner at a university, told FIFPro: "Before international games I would be taking drugs and partying with friends. Then days later I was trying to mark Lothar Matthaus or Ronaldinho.''
"I had and still have a lot of anxiety regarding performance. The pressure bottled up for years particularly when I captained different teams and had to be the face of the team when going through tough times. It was coupled with depression as well.
"I often went inside myself and only found release by going crazy on drugs and alcohol, until I realised I was on the verge of being addicted to drugs and getting wasted.''
Former U.S. international goalkeeper Jonny Walker, 39, spoke of the difficulties in leaving the professional game behind after retiring.
"One day you are on the pitch in front of 60,000 to 80,000 people," he said. "You are playing for your national team. You are doing interviews. Everybody is watching you.
"The next day it all stops. You are nothing any more. Nobody talks about you. Here today, gone tomorrow."
Information from the Press Association was used in this article.