The 30-year-old Everton midfielder - who has won 21 England caps - was taken to hospital on Sunday to be assessed after officers were called to Eccles Old Road in Salford.
Everton made a statement on Tuesday in which they said Lennon was “currently receiving care and treatment for a stress-related illness.”
Greater Manchester Police said: “Police were called at around 4.35pm to reports of a concern for the welfare of a man on Eccles Old Road.
“Officers attended and a 30-year-old man was detained under Section 136 of the Mental Health Act and was taken to hospital for assessment.”
The Leeds-born star made 43 appearances for his hometown club before being sold to Tottenham in the summer of 2005. He went on to make more than 360 appearances at the North London club before making the switch to Goodison Park for a reported £4m in September 2015.
He has since made 58 appearances for the Toffees, but has not featured in the line-up since February 21.
Football fans and fellow sports stars were quick to offer their support and sympathy after news emerged about Lennon late on Tuesday evening.
Stan Collymore tweeted: “Thoughts and love with Aaron Lennon and his family right now. I know that place, and I know he’ll be fine with good support from us all.”
Former Lancashire and England cricketer, Andrew Flintoff, also used his Twitter account to express sympathy, saying: “Lots of love and wishes @AaronLennon12 another cruel example of how mental illness can effect anybody , get well soon x #TimetoTalk”