Football fans suffer severe withdrawal symptoms and depression when the season ends, say researchers.
Manchester United celebrate winning this year's Premiership
They suggest the football-free summer could leave up to two thirds of football fans - 9.2m people - with "end of season affective disorder".
They will be particularly blue this summer as football has come to a halt after almost 22 months of uninterrupted matches - including last year's World Cup.
Those close to football supporters should look out for signs of depression, lethargy, inability to
converse and a feeling of hopelessness - feelings which may also be common during the season, if their team is not faring well.
Often fans will feel a void, an emptiness or loss on a Saturday afternoon
John Castleton, Psychologist
Other symptoms of the 'disorder' may include an inability to focus, a lack of direction and irritability - which may also be seen during the season when attempts are made to distract a fan from a match.
Being "as sick as a parrot" is not listed as one of the symptoms.
Two thousand fans completed the internet questionnaire for the survey commissioned for Barclaycard.
Researchers also held three focus groups and carried out face-to-face interviews with 29 football fans.
Three quarters of fans said football was more important than anything else, while 70% said it was their main conversational topic.
Football dominated supporters moods, with 83% saying it made them feel better and 86% saying they planned their days around big matches during the season.
Psychologist John Castleton, who wrote the report, said: "Dependence is part
of the human condition, we depend on our family, friends, interests and jobs to
construct our identity and give meaning to our lives.
"Football fans clearly hold a deep rooted relationship with their team, and
as a result - like any other close bond - to have that central pillar suddenly
removed, could cause a quite obvious existential crisis.
"Often fans will feel a void, an emptiness or loss on a Saturday afternoon."
He said around 10% said they were relieved the season was over, but the majority did feel something was missing.
Dr Castleton said: "There is obviously a great deal of passion - and where there is passion, there is loss."