The Nordic countries top the polls as the happiest in the world, but the assumption that life in Scandinavia is all bicycles and big smiles disguises the sadness of a significant minority of young people, it has emerged.

Among those in Denmark, Finland, Norway, Sweden and Iceland who do not say that life is good, some of the largest numbers are among the young – and particularly young women. While the reasons will vary from one individual and one country to another, it is thought that stress, loneliness and feeling under pressure to succeed may be playing a large part in their unhappiness.