Ohio Attorney General Mike DeWine said the confirmation came after state lab technicians worked through the night to expedite tests on DNA taken from the suspect, The (Cleveland) Plain Dealer reported.
Such tests normally take 22 days, DeWine said.
Experts in dealing with extreme trauma say the mother of the girl born to Castro, Amanda Berry, and two other women freed this week after 10 years of captivity can recover from such extended abuse.
Therapy tailored to the women's specific situations, privacy and time can help them rebound, The New York Times reported Thursday.
"For people who believe that it's inevitable that a horrific experience like this would leave lasting scars, the evidence does not necessarily support that," said Dr. Judith A. Cohen, medical director of the Center for Traumatic Stress in Children and Adolescents at Allegheny General Hospital in Pittsburgh.
Recovery may not come easy. About two-thirds of children who are kidnapped or abused have lingering psychological issues such as depression and post-traumatic stress disorder, studies suggest.
About 80 percent of abuse victims are significantly helped after about three to four months of therapy focused on the trauma they underwent. Some continue to have problems, though, if they had emotional difficulties before abduction, studies have found. Others such as Elizabeth Smart and Jaycee Dugard have gone on to help other abuse victims.
The women in Cleveland may have bonded during their long captivity and provided support for each other, said Dr. Terri L. Weaver, a psychology professor at St. Louis University.