Onset Patterns

Recently, our understanding of how the first signs of autism emerge has changed. The traditional notion was that there were two broad onset patterns. 

The most common course involves early signs of developmental differences, before 12-18 months of age. In approximately a third of cases, however, symptom onset does not occur until sometime in the second year of life, between 14 and 24 months of age (Fombonne, & Chakrabarti, 2001; Lord, Shulman, & DiLavore, 2004), after a developmental regression, or loss of previously acquired skills. The most frequently reported skill lost is language, although virtually all children who lose language lose social behaviors as well, such as eye contact, social interest, and engagement with others (Ozonoff, Williams, & Landa, 2005). However, more recently, we have come to realize that these two onset patterns do not capture all of the different ways autism emerges. 

There seem to be different patterns of late onset of symptoms - regression and plateau - though it is often difficult to separate children who show a regression (skill loss) from children who show a developmental “plateau,” marked by a failure to progress and transform simpler behaviors into more advanced social and communication skills (Chawarska et al., 2007; Siperstein, & Volkmar, 2004). Moreover, many children with a reported regression already have a number of developmental delays prior to the regression itself (Goldberg, Thorsen, Osann, & Spence, 2007; Ozonoff et al., 2005; Siperstein, & Volkmar, 2004; Werner, Dawson, Munson, & Osterling, 2005), and some children with clear signs of autism in the first year of life also experience skill loss in the second year (Werner, & Dawson, 2005). 

Some have suggested four different onset patterns: early (before 12 months) onset of symptoms without skill loss, late onset of symptoms seen in skill loss (regression) without early symptoms, early onset combined with later skill loss, and late onset without skill loss (developmental plateau) (Ozonoff et al., 2010). 

Another way to think about how autism begins is that children may reach the threshold for diagnosis at different points in the first three years of life, involving different amounts and/or combinations of early signs, slowing development, lack of progression, and frank losses (Landa et al., 2007; Rogers, 2009; Ozonoff et al., 2010). 

View two videos that illustrate the two traditionally defined patterns of onset:

Video 1: Onset in the First Year of Life

Video 2: Onser After Regression

Remember that not all children will fall into these categories or that failure to display these kinds of trajectories does not rule out an autism diagnosis.