[AlexanderNull]

This research doesn't claim to show any cause of ADHD, it's only showing potential exacerbating influences on, or at least confounding factors of, the severity of symptoms those with ADHD present later in life. Children who expressed more negative emotional outbursts were more likely to be mistreated later, and those that were mistreated were more likely to express ADHD symptoms, and those those expressed more ADHD symptoms were more likely to be mistreated. There's no causal explanation expressed there, simply correlations that could be used to identify at risk factors earlier on in life. Everyone expresses their ADHD differently and identifying patterns in life that may either aggravate or alleviate the difficulties of the condition can potentially be helpful in the long run.