The chief medical officer, Dame Sally Davies, recently called for more support for mental health services in her annual report, which highlighted how mental illness led to the loss of 70 million working days last year—an increase of 24% since 2009.

Of particular importance is the report’s call for improved support for young people with mental illness. More than 50% of adult mental health illnesses develop during adolescence, but the diagnosis is often missed at this stage and not picked up until many years later. GPs have an important role in supporting parents and picking up on any early warning signs—distinct from “normal” adolescent moods—so that they can act accordingly.

The adolescent experience, when it gets an airing in the media, is often portrayed as an angst filled, difficult time. However, most adolescents are just getting on with growing up, studying hard, and finding out about life in undramatic non-shocking ways. Indeed, 90% of adolescents complete the transition to adulthood successfully and without posing any mental health challenges or untoward parental challenges. GPs and parents should therefore be alert to any considerable mood changes as serious indicators of possible mental health problems.

When an adolescent “goes off the rails” it is usually obvious to those around them; irritability, anxiety, social withdrawal, inexplicable challenging behaviour, or a plunge in academic achievement are all big indicators. This may leave everyone feeling uneasy and unsure of how to respond or what to say. Fear of upsetting the young person and uncertainty over whether a behaviour change is “just an adolescent thing,” distress, or a sign of mental illness, leave concerned adults looking on with a sense of helplessness. If everyone involved just skirts around the changes, then all sorts of ideas can grow in everyone’s minds about how dangerous or unstable the young person is becoming, which just adds to the general anxiety.

The onset of mental illness in adolescence is often gradual, and the young person may not know how to describe in any detail the sense that “I no longer feel my normal self.” Such a change is frightening, and it is natural to want to deny anything is wrong, or to try to prove to themselves and others that they are still alright. Therefore, teenagers are unlikely to seek help from their GP and are more likely to show their distress through their behaviour, which they rely on others to pick up on and to respond to.

The earlier a problem is picked up, the sooner help can be offered. Engaging a young person in a discussion about themselves can feel daunting, even for their GP. However, many young people will appreciate someone taking a genuine interest and talking to them directly about what might be going on. This in itself will demonstrate that such “strange” experiences can be named and talked about, and that what is happening can be understood and worked with.

What is needed in such a situation is some straight talking. Even if the young person reacts with a “there is nothing wrong,” to a straightforward enquiry (“I’ve noticed you are . . . are you alright?”) the message is someone has noticed and cares enough to ask. This is the first step in opening a discussion, and allowing a space where if the young person is ready to talk then they know they can.

They too may well have become frightened by any change they feel in themselves—a low mood, or the impulse to be angry and lash out—and feel that they have no control over what is happening to them. It gives them relief to know this has been noticed, can be talked about, and that there are things that can be done to help.

So it is best to be direct: a concerned adult should say what they have noticed and that they are willing to talk about what might be going on. If they really cannot bring themselves to do this, try to ensure someone else can. Adolescents are still at the stage of looking to adults for the lead, especially when it comes to new situations, and they are likely to respond well to clear guidance and honesty.

The earlier any problems are addressed and confronted head-on, the more likely a diagnosis and appropriate treatment programme can begin. The weight of responsibility for preventing a late diagnosis lies with medical professionals, who must work closely with schools and parents to encourage action.

Alex Horne is the consultant child and adolescent psychiatrist at Nightingale Hospital.

Competing interests: I declare that I have read and understood the BMJ policy on declaration of interests and I have no relevant interests to declare.