Young Researcher Passionate About Helping Youth Through Innovation

Child psychiatry researcher Paul Croarkin, D.O., has set his sights high to make a difference in the lives of children and adolescents with mental illness. And he’s well on his way to doing so, say colleagues.

Of the over 200 residents, clinical research fellows, and junior faculty researchers who have been mentored by Mark Frye, M.D., chair of psychiatry at the Mayo Clinic in Rochester, Minn., “Dr. Croarkin is in the top 1 percent. Paul’s energy, commitment to the field, and research potential are refreshing. I am confident that his research will impact the field and transform the practice of pediatric mood disorders.”

Others apparently agree with that assessment: Croarkin is the winner of the Depression and Bipolar Alliance’s 2015 Gerald L. Klerman Young Investigator Award, which was presented at APA’s annual meeting in May in Toronto.

Croarkin was born in Columbia, Mo., in 1971. Both his parents played a role in his future career. His mother was a math teacher and his father was a school administrator and, as Croarkin recalled, “a backyard psychologist of sorts. … Just listening to the things he did in the course of his job got me interested in child psychiatry.”

During clinical rotations at the Texas College of Osteopathic Medicine, he liked internal medicine, neurology, and emergency medicine, but enjoyed psychiatry the most, he said. “I didn’t want to go home at night; it was so much fun. I especially enjoyed developing and honing interview skills. I was also inspired by the amazing discoveries being made in genetics and neuroscience—discoveries that I knew would undoubtedly impact psychiatry. Psychiatry is, in my opinion, the final frontier of medicine. There is so much to do in terms of research.”

After he graduated from the Texas College of Osteopathic Medicine in 1998, he pursued a general psychiatry residency at the Naval Medical Center in San Diego from 1999 to 2002. Subsequently, he worked as a staff psychiatrist for the Navy for three years. “Somewhere along the line,” he said, “I realized that I wanted to pursue child psychiatry training and an academic career.” He entered a training program for child and adolescent psychiatry at the University of Texas Southwestern Medical School in Dallas, finishing there in 2007.

From 2007 to 2011, Croarkin worked at the University of Texas Southwestern as a clinical child psychiatrist, but it was research in that domain that especially attracted him. So he followed that muse and also obtained a master’s degree in clinical research.

In 2011, Frye recruited Croarkin to the Mayo Clinic. Today he is devoting about 75 percent of his professional time to child psychiatry research.

“I find the scientific process a creative, wonderful thing,” he said. “It is what gets me up at 4 or 5 in the morning to come to work. And frankly, there is ample room for improvement in what we psychiatrists can offer our patients, particularly our young ones. Thus I’m hoping that, in some small way, I can improve the tools that clinical psychiatrists need to help young patients.”

Seeking Biology of Depression

One of Croarkin’s research goals is to better understand the biology of adolescent depression. A pilot study that his group published in the March 2013 JAMA Psychiatry suggests that youth with major depressive disorder have excessive N-methyl-D asparate (NMDA)–mediated glutamatergic neurotransmission. Glutamate is the major excitatory neurotransmitter in the brain.

Croarkin and colleagues are now executing a larger study to test this hypothesis and determine whether glutamate activity can identify the depressed youth who will respond to an antidepressant and those who will not.

Croarkin is also working with colleagues to determine whether pharmacogenomics profiling might be used to improve antidepressant treatment in depressed and bipolar youth. The platform they are using is called GeneSight Psychotropic With Mood Stabilizers. It determines, in a particular patient, which variations of eight genes known to influence antidepressant metabolism and response are present.

Their study includes a broad spectrum of teens who meet criteria for major depression or bipolar disorder. The GeneSight Psychotropic With Mood Stabilizers panel will be used to obtain a unique pharmacogenomics profile for each of the enrolled patients. The teens will then be randomized to one of two groups. In one group, the clinician will have their GeneSight results to guide antidepressant treatment decisions; in the other group, the clinician will not. “Then we’ll compare the outcome for both groups at four weeks, eight weeks, and six months later to see whether it was beneficial having the clinician use the GeneSight results,” said Croarkin.

In fact, multiple clinical studies conducted by other researchers have found that when clinicians used GeneSight to help guide treatment decisions, patients were twice as likely to respond to the selected medication. Many psychiatrists around the United States are already using pharmacogenomics testing.

Research on rTMS Offers Promise

Existing evidence supports repetitive transcranial magnetic stimulation (rTMS) as a treatment for adult treatment-resistant depression. This brain stimulation modality is approved by the Food and Drug Administration for adults and used clinically in many areas of the United States. But can rTMS also help youth with treatment-resistant depression? A small study that Croarkin and his group conducted suggests that it can.

“We have an ongoing sham-controlled trial and are currently developing additional trials to test this possibility. We are also studying the effect of rTMS on the glutamate neurotransmitter system to better understand the mechanisms of action and to develop biomarkers to predict response to rTMS at baseline,” he said.

Indeed, if there were only one thing that he could achieve during the next five years, it would be to make rTMS a viable treatment option for youth with treatment-resistant depression, Croarkin indicated.

“We have a long way to go, however,” he said. “We’ll need more input from basic scientists and biomedical engineers to develop new forms of stimulus delivery and, ultimately, individualized approaches that target certain regions of the brain.”

Croarkin’s single-mindedness to help children and adolescents with mental illness will undoubtedly lead him to achieve that ultimate goal.

“As his mentor, I can state with confidence that Dr. Croarkin is a very intelligent, highly motivated young researcher who is focusing his research on complex childhood neuropsychiatric disorders,” said Mustafa Husain, M.D., vice chair of psychiatry at Duke University. “His work will help us understand the etiopathology of these complicated behaviors and eventually lead to neuromodulation therapies.” ■