Chawarska’s view echoes the findings of numerous studies that reveal a “range of onset patterns,” as University of Melbourne autism researcher Amanda Brignell and her colleagues explain in a 2016 paper, from ‘early onset’ (early developmental delays, no loss of skills) and ‘delay and regression’ (some early delays, then loss) to ‘plateau’ (no early delays and no loss, but a failure to gain) and ordinary ‘regression’ (no delays before a clear loss). These trajectories differ so much in their timing, speed, depth and effects that it requires a tangle of words and parentheticals to try to squeeze them into a binary framework.
Given all this, Ozonoff argues, we should speak not of regression, but of a variety of onsets: The true clinical picture of how autism begins to present is not two-tone or even spectral, but a complex kaleidoscope of possibilities. “I don’t even call it regression anymore,” she says. “I just think of it as onset: how symptoms start.”