SAN FRANCISCO – It’s easy to find someone willing to take your money for a brain scan. It’s a lot harder to use these scans in understanding mental illness, according to Dr. Robert L. Hendren.
"We can’t really find the kind of images that can help us make the diagnosis of a mental disorder," said Dr. Hendren, director of child and adolescent psychiatry at the University of California, San Francisco. Genetic, metabolic, and other kinds of screening for biomarkers are only slightly more useful, he said at the annual meeting of the American Academy of Pediatrics.
It still makes sense to look for biologic causes for mental illness. "Increasingly, we’re finding that disorders like conduct disorder have a neurological, neurodevelopmental etiology," Dr. Hendren said. After all, brains grow and change as they interact with the environment.
And physicians need better tools for diagnosing such illnesses. Signs and symptoms don’t always fit neatly into the categories laid out in the Diagnostic and Statistical Manual of Mental Disorders.
So researchers have tried MRI and other approaches to look for patterns that might reveal mental illness. They have found some correlations.
And some imaging centers have leaped on these findings to market their services to families of children with mental illness. "You probably are aware of people doing that," Dr. Hendren said. "Families will pay $3,000 or $4,000 to have these scans performed and shown to them. And then they get recommendations based on a good history that aren’t much different than if the scans had not been done."
The problem is that researchers have not traced any common diagnosis to a particular site in the brain. Multiple sites may be involved.
Imaging can help only in very specific instances. Among the accepted indications for MRI include microcephaly, macrocephaly, unusual head shapes, regression, or an abnormal neurologic examination.
Some of the same limitations that apply to MRI apply to other types of tests for biomarkers. Researchers have realized that no single gene is responsible for autism, schizophrenia, or most of the other common mental disorders. "We’ve learned that these are very complex disorders with multiple genes involved," Dr. Hendren said.
But when there is reason to believe genes are involved, genetic testing might be in order. For example, he said some experts recommend a comparative genomic hybridization array for various intellectual disabilities, developmental disorders, and autism. Autistic children also might benefit from further genetic tests, including a test for fragile X, since about 3% have this genetic condition.
Other authorities have recommended a chromosomal microarray for patients with developmental delay, intellectual disabilities, autism spectrum disorder, or multiple congenital anomalies. For patients with clear chromosomal rearrangements – or a family history of these rearrangements, or multiple miscarriages, G-banded karyotyping might be in order, Dr. Hendren said.
Metabolic screening also can yield some information about mental disorders, but is really worthwhile only in patients with clear signs of metabolic disorder, such as a history of lethargy, cyclic vomiting, early seizures, dysmorphisms, mental retardation, or regression. And if these tests are a part of newborn screening – as they often are –there’s no need to repeat them, he said.
Some authorities also recommend a complete blood count for mental disorders. Naturally, other tests, such as thyroid function, serum organic and amino acids, serum lactate and pyruvate, lead screening, iron deficiency, methyl CpG binding protein 2, and Wood’s lamp, might prove helpful when specific conditions are expected,. Most other tests are more controversial.
So while waiting for researchers to find a high-tech solution for diagnosing mental illness, what can physicians do to identify mental illness in their patients? "Evaluation should be guided by in-depth history and family history, and a good physical examination," Dr. Hendren said.
He said he has received funding for clinical trials from Forest Laboratories, BioMarin, Curemark, the National Institute of Mental Health, and Autism Speaks.