As they become adolescents, it is true that most people with PWS do not usually reach full sexual development, and there have been only three recorded cases worldwide of a woman with PWS having a child. However this might be misleading as there may be cases of which doctors are unaware.

People with PWS are individual in their growth pattern, and there is no set way in which they could all be said to develop. Some, start to develop sexually at a young age, but for most, puberty is delayed until late teens. Men with PWS typically have a small penis, and undescended testes are common. Pubic and facial hair may be underdeveloped and sparse, and the voice change may not occur. In women, breast development is often small, and menstruation, if it does occur, is often irregular.

Teenagers with PWS do not experience the growth spurt which usually occurs in early teens and hence tend to be a few inches shorter than the average: men about about 5'2" (155cm) and women about 4'10" (145cm). Growth hormone treatment can be given to help with growth and muscle tone, and sex hormones (both male and female) to help with sexual development, but this will depend to some extent on the individual's existing hormone levels. Behavioural and eating problems may become more challenging during the teens and early twenties and it is often very difficult for the families of PWS sufferers to cope with them at this stage.

As they become adults, people with PWS have varying abilities in attaining independence, although all will need some form of support or monitoring to help with controlling their food intake, and thus their weight.

Despite the fact that many individuals have the intellectual and physical ability to work, they are usually ill-equipped on an emotional and social level to deal with the stresses and demands of the ordinary workplace. However, they can make a positive contribution to society in many ways and may be involved in voluntary work, craft work, or can usually have a part-time job. Many PWS affected people live with their families, but an increasing number live in residential homes, or being supported to live in the community. In the past, life expectancy was short because of health problems associated with massive obesity, but nowadays life expectancy is increasing because of better dietary management and better understanding of the problems associated with PWS. The oldest known person with PWS in the UK is a woman aged 72. Whilst cancers and strokes are not so common in older people with PWS, mental health problems may increase with age.

Apart from various hormone treatments and some surgical intervention (eg, to bring down undescended testes where they occur, there is no real cure or treatment for PWS. There have been many advances in the fields of genetics, but it is likely to be several years before the genes which are involved in PWS are fully identified. No drug so far has proved to be of lasting help with regard to suppressing the raging appetite experience by PWS sufferers.

Severe challenging behaviour and some mental health problems have responded relatively successfully to drug treatment, but dosages need to be carefully monitored. Generally speaking lots of the adverse effects of the syndrome can be lessened by good dietary management, exercise programmes, good general health care, and by good general management of behaviour and education. The help of a dietitian, paediatrician, physiotherapist, educational psychologist, and maybe, if needed a speech therapist should be sought as soon as a diagnosis is made