A number of studies in recent years have shown an association between childhood abuse or traumatic events and ADHD. A study published in the Journal of Aggression, Maltreatment & Trauma in March, 2014, concludes, "...the odds of ADD/ADHD are sixfold greater for those who report they were physically abused in childhood""  This study, as well as other studies, have not been able to discover the why this link exists.
There seem to be four possible explanations for the correlation between abuse and ADHD: signs of abuse are being misdiagnosed as ADHD, children with ADHD misbehave more often and are more difficult to discipline and this can lead to abuse, parents of children with ADHD are more likely to have ADHD and this can cause them to overreact to behavior problems or because abuse and trauma can cause changes in the brain it leads to creating symptoms similar to ADHD.
Theory 1: Sign of Abuse are Misdiagnosed as ADHD
According to Safe Horizons, and advocacy and service organization for victims of abuse, some of the signs of childhood abuse include difficulty sleeping, problems focusing or concentrating, poor school performance, risk taking or impulsive behaviors. As you can see, many of the signs of abuse overlap with symptoms of ADHD.
Theory 2: Children with ADHD Misbehave More Often and Are More Difficult to Discipline
Any parent of a child with ADHD will confirm that discipline is a challenge. Children with ADHD often don't respond to traditional types of discipline because they have difficulty linking the behavior with the punishment, especially if they don't occur together. And while they don't necessary "misbehave," symptoms of ADHD can be frustrating. Children with ADHD often appear to not listen, are forgetful and act impulsively. ADHD experts sometimes list parent education as a necessary part of the overall treatment for childhood ADHD.
Theory 3: Parents of Children with ADHD are More Likely to Have ADHD and Overreact to Behavioral Issues
ADHD is passed down from parent to child, which means if a child has ADHD, there is a high probability that at least one parent also has ADHD, even if never diagnosed. Adult ADHD has been associated with problems in jobs, careers and relationships. They are more likely to be divorced or separated and have dysfunctional interactions with their children than those without ADHD. They often feel incompetent and isolated. Comorbidities such as depression and anxiety increase feelings of inadequacy and make it more difficult to cope with the demands of parents.
Theory 4: Trauma from Abuse Changes the Brain and Causes Symptoms of ADHD
When abuse, physical or emotional, happens during the developmental years, changes to the brain can occur. These changes might increase the likelihood of developing ADHD and other psychiatric problems, such as post traumatic stress disorder. Trauma, especially during early development, may contribute to actually changes in brain chemistry and functioning, creating ADHD-like symptoms.
Certainly, if abuse does play a role in some cases of ADHD, it is not the only cause and it is damaging to both parents and children to jump to the conclusion that because a child has ADHD there is a good chance of some prior abuse. One of the myths surrounding ADHD is that "it is the parent's fault" although that sentiment usually pointed to lax parents who didn't bother disciplining their children. While theses studies are important and can provide an immense amount of information on why there is a high rate of abuse reported by those with ADHD, it will not help if critics use this information to focus again on "its the parents fault" and this time point to abuse rather than lax parenting.
More research is definitely needed. When 30 percent of adults with ADHD reporting childhood abuse, something is wrong. Looking for answers and ways to stop abuse is good thing. Even one abused child is too many suffering at the hands of others.
 "Establishing a Link Between Attention Deficit Disorder/Attention Deficit Hyperactivity Disorder and Childhood Physical Abuse," 2014, March, Esme Fuller-Thomson, Rukshan Mehta and Angela Valeo, Journal of Aggression, Maltreatment & Trauma, Volume 23, Issue 2
"Linkages Between Child Abuse and Attention-Deficit/Hyperactivity Disorder in Girls: Behavioral and Social Correlates," 2006, Allison M. Briscoe-Smith and Stephen P. Hinshaw, Child Abuse & Neglect, Volume 30, Issue 11
"News Analysis: Are We Misdiagnosing Childhood Traumas as ADHD?" 2014, May 6, Rachel Barclay, Healthline.com