Advances in Mental Health and Intellectual Disabilities

Purpose – This paper seeks to discuss the complexity of the relationship between genotype and phenotype and highlight the importance of a greater understanding of behavioural phenotypes in genetic syndromes. The aim is to explore the developmental trajectory of the behavioural phenotypes as individuals emerge from childhood into adulthood and beyond.

Design/methodology/approach – Information was gathered from a search of the relevant literature over the past 20 years using Medline and PsycINFO databases in May 2010 as well as information published in textbooks on this matter.

Findings – The outcomes were considered under five areas of functioning: cognition, communication, behaviour, social functioning and propensity to psychiatric illnesses. The research thus far suggests that outcomes in behavioural phenotypes in adults are extremely variable. Individual predictions are difficult to make. However, some trends do emerge.

Originality/value – Findings of particular interest are the rates of attention deficit hyperactivity disorder and autism spectrum conditions and how these change over the developmental trajectory. The paper highlights the need for further research in this area and discusses the need to view behavioural phenotypes as a continuum across the lifespan.