Can Autism be Detected at 18 Months?

4—8per 10000 infants develop autism (Gillberg et al, 1991).Given its rarity, it appearsuneconomical to attempt early detection in a random sample. A basic tenet of the present study is that the early detection of autism is both possible and economic. It is possible because findings from experimental psychology have shown us what to look for in toddlers if we want to detect autism early. Firstly, pretendplay (m which objectsareusedasif theyhave other properties or identities and which is normally present by 12—15 months) is absent or abnormal in autism (Wing & Gould, 1979;Baron-Cohen, 1987). This deficit seemsto be highly specific there is not a generalabsenceof playper se.For example,children with autism do show functional play (using toys as they were intended to be used) and sensorimotor play (exploring the physical properties of objects only, with no regard to their function, e.g. banging, waving, sucking, throwing, etc.) (Baron-Cohen, 1987). Secondly, joint-attention behaviour (normally presentby 9—14 months old) is also absentor rare in autism (Sigman et al, 1986). Again, this is a strikingly specific deficit. For example, while the joint attention behaviour of protodeclarative pointing is absent or rare in autism (Baron-Cohen, 1989), pointing for †̃¿ non-social' purposesis present.Thus, theydo showprotoimperativepointing (Baron-Cohen, 1989), and pointing for naming (Goodhart & Baron Cohen, 1992). (Joint-attention behaviour includes pointing, showing, and gaze monitoring, and is defmedasattemptsto monitor or direct the attention of another person to an object or event: proto declarative pointing is the use of the index finger to indicate to another person an object of interest, as an end in itself; protoimperative pointing is the use of the index finger simply to attempt to obtain an object; pointing for naming is to pick out an object within an array while naming it, and this canbenon social.) Other deficits in joint-attention in autism include a relative lack of showing objects to others, and of gaze monitoring —¿ directing one's gaze wheresomeoneelseis looking (Sigmanet al, 1986). Sinceboth pretendplay and joint-attention behaviour, especially protodeclarative pointing, are universal development achievements (Butterworth, 1991; Leslie, 1991),normally presentin simpleforms by 15 Autism Is currently detected only at about three years of age. This study aimedto establishIf detection of autism was possible at 18 months of age. We screened 4118-month-old toddlers who were at high genetic risk for developing autism, and 50 randomly selected 18-month-olds, using a new Instrument, the CHAT, administered by GPsor health visItors. More than 80% of the randomly selected 18-month-old toddlers passed on al Items, and none failed on more than one of pretend play, protodeclarative pointing, joint-attention, social Interest, and social play. Four children in the high-risk group failed on two or more of these five key types of behaviour. At follow-up at 30 months of age, the 87 children who had passedfour or more of these key types of behaviourat 18 months of age had continuedto develop normally. The four toddlers who had failed on two or more of these key types of behaviour at 18 months received a diagnosis of autism by 30 months. British Journal of Psychiatry(1992),161,839—843