A new literature analysis showed that probiotics improved depression, cognition, anxiety and even social anxiety although there needs to be more reasearch done including more placebo controlled trials, (Caroline J. K. Wallace and Milev Roumen, "The Effects of Probiotics on Depressive Symptoms in Humans: A Systemic Review," Annals of General Psychiatry (2017) 16, No.14 doi: 10.1186/s12991-017-0138-2). Changes in the mircobiology of the gut may have profound effects.
Ten studies were analysed for depression, seven for anxiety and three for cognition. Depression and anxiety can manifest as increased health dangerous behaviors in individuals with autism. One study in the analysis found a reduction in anger-hostility scores on a standaridzed outcome measure. Individuals with autism often have problems coping with emotions including anger. One placebo controlled study discussed in the analysis showed "reduced overall cognitive reactivity to depression, in particular aggressive and ruminative thoughts." Ruminative thoughts are common in individuals with autism spectrum disorders. Unlike medications, probiotics have not shown to have side effects.