Premature babies are more likely than others to develop significant mental health problems, including ADHD, depression and anxiety, according to a new study.

McMaster University researchers discovered that steroids, often provided to mothers about to give birth to a premature baby, can be even more harmful to the baby in later life. Preemies born from mothers given steroids go on to develop alcohol and the other substance abuse problems more often than their peers, the study found. Psychiatric problems were found to be three times more likely among preemie babies, compared to those born at normal weights. When steroids are provided to mothers, that risk is four-and-a-half times more likely than normal.

"Even if these steroids increase the risk of something like ADHD, if they don't take the steroids in some cases they might not have the child," Ryan Van Lieshout of McMaster University, said.

Premature babies are often born severely underweight, and can perish soon after birth. According to a 2012 report from the World Health Organization (WHO), nearly seven percent of premature babies around the world die. That mortality rate is just around 0.5 percent in Canada. However, other significant health problems can be experienced by people born before their mother comes to full term. These include learning disabilities, as well as problems with vision, hearing and breathing.

Researchers examined case histories of 84 adults, born as premature babies between the years 1977 and 1982. These records were then compared to 90 adults who were born at full term, at normal weights. The group of preemies were found to exhibit ADHD more often as teenagers, and anxiety was more prevalent when they reached their 20's, according to the study.

It is uncertain what causes are responsible for the increase in disorders among premature babies. Parents of preemies are often more protective than normal, which could alter the way the children are raised. It is also possible that severe stress placed on newborn brains could also be responsible for the rise of problems later in life.

"Importantly, we have identified psychiatric risks that may develop for extremely low birth weight survivors as they become adults, and this understanding will help us better predict, detect and treat mental disorders in this population," Van Lieshout said. 

The study did not include genetic testing of the subjects, so it is impossible to determine the extent genetic inheritance played in the disorders, compared to environment.

Study of the risk of mental and physical disorders in preemies was published in the journal Pediatrics.