Joanna Fortune: My teen goes to bed late and then spends half the day in bed

He finds it difficult to get out of bed in the morning for school — I've tried talking to him but I'm not getting through

Dr Joanna Fortune: "It can be tempting to blame phones and late-night TV, which undeniably contribute to poor or late-night sleep. But beyond these factors, teenagers have 'night owl' tendencies, leading them to sleep later at night and get up later. You likely see this pattern on the weekends."

My teenage son's sleep is all over the place. He goes to bed late most nights and then finds it difficult to get out of bed in the morning for school. 

The weekends are worse — he spends half the day in bed and even longer if he meets his friends on a Saturday night.