Parenting Impact on Autistic Kids: You Can't Have Your Cake and Eat It Too
Now, of course, we know this is nonsense, and very hurtful to the mothers who were so unjustly blamed. Parents of autistic kids don't consistently differ from parents of non-autistic kids in their parenting skills. But many people in the autism community* go too far in the opposite direction - denying any impact of parents on their autistic kids.
What they don't seem to realize is that if parenting styles don't affect autistic kids, then a lot of autism therapies would also be useless, because these therapies involve deliberately and systematically doing things that some parents do on their own.
The easiest example is relational therapies such as DIR and Floortime. The interactional style that the therapists take in these therapies is pretty much the same as the parenting dimension known as 'parental sensitivity' - a very well studied parenting dimension that has a lot of important implications for child development in both typical and disabled children. Parents high in parental sensitivity tend to have children who are more securely attached, have fewer behaviour problems, have better social-cognitive skills, and even have slightly better language skills (especially if they have a disability affecting language development, such as deafness).
Based on this, we would predict that an intervention mimicking sensitive parenting behaviour should reduce behaviour problems, improve social skills, and improve language development, as well as improving attachment security. At least two of those effects has been documented as a result of relational therapies, with this study, this study, this study and this study all finding improvements in social skills and this study finding improvements in expressive language in autistic children receiving relational therapies. But in order for this treatment to work, autistic kids must also be affected by naturally-occurring differences in parental sensitivity (such as differences due to the parent's own attachment style or marital conflict).
ABA is less easily equated to parenting styles, because there are two distinct aspects to ABA - direct teaching and prompting of skills, and consistent rewards and punishments to modify behaviour. In parenting styles research, those two components split up into separate domains of parenting behaviour.
The impact of consistent rewards and punishments has been very extensively studied under the dimension of consistent discipline. Children who get consistent discipline tend to show lower behavior problems and better attention and impulse control. So it stands to reason that ABA, which includes consistent discipline, would reduce behaviour problems, and the research supports this. But similarly, naturally occurring variations in how consistently parents discipline their children (such as differences due to parental depression) must also affect autistic children's risk of behaviour problems.
Parental teaching has been studied far less than consistent discipline. However, parental direct teaching is associated with improved emergent literacy skills, mathematics skills and earlier toilet training (most parents directly teach toilet training, but the parents who start earlier tend to have kids who are fully toilet trained earlier). So, at the very least, this suggests that ABA's direct teaching should improve academic skills and self-care skills. This study and many others have found that ABA improves self-care, but I couldn't find any data on ABA's impact on academic skills. Once again, if ABA can directly teach skills to autistic kids, individual differences in parents' tendency to directly teach skills must also affect their kids.
Almost all of the practices commonly used in autism therapy are also things that a subset of parents do on their own. So it's intellectually dishonest to simultaneously claim that these therapies can affect autistic kids' development and at the same time insist that naturally occurring differences in their parents' behaviour can't also affect their children. And if you claim those treatments can cure autism (a claim that isn't supported by the data, by the way), then parents who do the same things spontaneously should logically also be able to cure autism (or prevent it - a really early cure is indistinguishable from prevention).
If parents can't cause autism, they also can't cure it. And neither can a therapist who only does things that many parents do anyway.
* Note - I'm using 'autism community' to refer to the community of mostly parents and professionals, while 'autistic community' refers to the community of mostly autistic adults.