The Royal College of Psychiatrists (RCP) said all young patients should be asked about their screen time and viewing habits amid growing evidence of possible links between poor mental health and content seen online.
It said harmful online content such as images of self-harm or material promoting eating disorders could have an impact on an existing mental illness.
Conditions such as depression may also make children more likely to spend time online, while use of technology could lead to poor sleep, under-performance at school, behavioural problems and eating issues, it said.
Dr Bernadka Dubicka, chairwoman of the child and adolescent faculty at the RCP, said: “Although we recognise that social media and technology are not primary drivers of mental illness in young people, we know that they are an important part of their lives and can be harmful in some situations.
“As a frontline clinician, I regularly see young people who have deliberately hurt themselves after discussing self-harm techniques online.
“We’re also finding that some young people report being recommended harmful content; for example, links to websites encouraging weight loss or displaying self-harm after searching for, or clicking on, similar content just once before.”
Earlier this month, MPs said addiction to social media should potentially be classed as a disease as they called for new regulations to protect children from an “online Wild West”.
They said platforms such as Facebook, Twitter and Instagram should be regulated by Ofcom and forced to adhere to a statutory code of conduct.
Concerns have been growing about graphic online content, including material featuring suicide and self-harm.
Earlier this year, the father of 14-year-old Molly Russell, who took her own life in 2017, said Instagram had “helped kill” his daughter.
Claire Murdoch, national director for mental health at NHS England, said: “Social media plays a big part in everyday life for most children and young people but it should act as wake-up call when leading psychiatrists say online activities now need to be considered when assessing youngsters’ mental health and wellbeing.
A government spokesman said: “The government will shortly publish a White Paper which will set out the responsibilities of online platforms, how these responsibilities should be met and what would happen if they are not.
“We have heard calls for an internet regulator and to place a statutory ‘duty of care’ on platforms, and have seriously considered all options.”