More News About Genetic Risk for Bipolar Disorder
A change to just one base pair may increase the risk of early-onset bipolar disorder
In a 2017 article in the Journal of Clinical Psychiatry, researcher Paul E. Croarkin and colleagues describe findings from their study of genetic risk factors for early-onset bipolar disorder. The researchers focused on single nucleotide polymorphisms (SNPs), which are variations in a single base pair of a DNA sequence. SNPs are normal variations or copying errors that occur when DNA is replicated. Croarkin and colleagues tracked 8 SNPs that had been linked to bipolar disorder in previous studies. They examined 69 patients from a study of early-onset mania, 732 adult patients with bipolar disorder (including 192 with early-onset illness), and 776 healthy controls. The researchers compared patients with early-onset illness to controls, and also looked for connections between specific SNPs and early-onset illness.
The SNPs analyzed in the study map to three genes that have repeatedly been associated with the risk for bipolar disorder in other studies. These include CACNA1C (one of several genes that create calcium channels), ANK3, and ODZ4. Croarkin and colleagues determined that the presence of these SNPs, particularly the ones that involved the CACNA1C gene, were associated with early-onset bipolar disorder.
Editor’s Note: These findings may lead to better treatment for early-onset bipolar disorder. The CACNA1C calcium influx gene that has repeatedly been connected to bipolar illness can be blocked by the calcium channel blocker nimodipine. Nimodipine has lithium-like effects in mania and depression in adults. One case report by Pablo A. Davanzo in the Journal of Child and Adolescent Psychopharmacology described success using nimodipine and the thyroid medication levothyroxine to treat a 13-year-old boy with very rapid cycling bipolar disorder that had previously failed to respond to multiple medications.
Nimodipine deserves further study in children showing symptoms of bipolar disorder. The company Genomind provides testing for the CACNA1C gene. We hope it will soon be determined whether the presence of this SNP predicts a good response to nimodipine.
Being able to predict who will get bipolar disorder is a long way off. However, there are some clear risk factors. Young people from families that have had several generations of bipolar disorder or related disorders are at increased risk for bipolar disorder. This risk increases for children who experience adversity in childhood, such as abuse or neglect. The presence of early mild symptoms of mania, depression, or disruptive behavior further increase this risk.
For doctors, a patient’s clinical history of these three types of risk factors can help identify whether they are at increased risk of developing bipolar disorder. Patients with several risk factors should be observed closely and treated with psychotherapy or medication as needed.
Parents of children between the ages of 2 and 12 who have shown some signs of mood or behavioral symptoms are encouraged to join our Child Network. We provide a secure online platform where parents record their children’s symptoms of anxiety, depression, attention-deficit hyperactivity disorder (ADHD), oppositional behavior, and mania on a weekly basis. Symptoms are charted over time in a graphical depiction that can be shared with the child’s doctor. For more information, see page 11 of this issue. To join, visit our website bipolarnews.org and click on the tab for the Child Network.
