Preemies are more likely to develop psychiatric problems such as anxiety, depression and attentive-deficit/hyperactivity disorder (ADHD), says new research from McMaster University.

It also showed life-saving steroids taken by mothers before giving birth to preemies — babies born prematurely at extremely low birth weights — also had a significant impact: without them, children are less likely to develop alcohol dependency and substance abuse problems. With them, any protection from alcohol dependency disappears, and the prevalence of psychiatric problems in preemies is amplified.

Published Monday in the journal Pediatrics, lead author Dr. Ryan Van Lieshout said the research will "help us better predict, detect and treat mental disorders in the population."

Mental health problems 3 to 4.5 times more likely

Globally, one in 15 preemies dies according to a World Health Organization study from 2012. In Canada, their mortality rate is significantly lower at just five deaths for every 1,000 births. Physiological problems are abundant and include problems in sight, hearing, breathing and an increased likelihood of learning disabilities.

Van Lieshout's research focused on their mental health, and showed preemies are three time more likely than normal birth weight babies to develop psychiatric problems. When prenatal steroids are used, that number jumps to four and a half times more likely.

Without the steroids, preemies are three times less likely to develop an alcohol or substance abuse disorder.

Van Lieshout, a McMaster University assistant professor in psychiatry and behavioural neurosciences as well as the Albert Einstein/Irving Zucker Chair in Neuroscience, said the research is not intended to persuade mothers to avoid steroids to help preemies.

"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," Van Lieshout said.

Cohort has been studied for 30 years

The research looked at 84 adults born between 1977 and 1982 who were born weight under one kilogram (two pounds, two ounces), and compared them with 90 babies of normal birth weight.

The cohort has been monitored from birth, and is now in their 30s. Van Lieshout said in their teens, the preemies were more likely to be shy or have attention problems such as ADHD. In their 20s, the group was more likely to have anxiety disorders.

He said their model did not include genetic testing so Van Lieshout is not able to identify how much of a role the child's DNA plays into the findings, and how much of their results are because of how the children were raised.

Both may be at play, but Van Lieshout said there are many theories on the subject including that preemies have more protective parents and that their brains and bodies go under substantial stress when born underweight, which may have an impact on their brain development.

The reasons why preemies are predisposed for these mental health disorders, and sometimes protected from substance abuse, remain an "open question" to Van Lieshout. He does not think it should be considered as a recommendation against steroid treatment.

"These are lifesaving treatments," Van Lieshout said. "Without these treatments many of these infants might not have survived."