The field of neuromodulation encompasses a wide spectrum of interventional technologies that change electrochemical activity within the central nervous system in order to elicit a therapeutic effect.
The oldest and best known of these modalities, and the one with the infamous reputation, is electro-convulsive therapy, which, in spite of Hollywood’s barbaric portrayal, is quite effective (and not painful) in treating refractory depression.
Within the discipline of addiction medicine, which relapse is now the norm rather than the exception, reliance on current therapeutic modalities, including Medication-Assisted Treatment (MAT) have not significantly improved outcomes in the general population. This has resulted in significant increases in morbidity and mortality, creating a significant public health crisis.
Nearly 20 years ago, advances in neuroimaging helped illuminate the process of functional neural-anatomy, neurobiology and specific pathologies including addictive disease and mood disorders. More recently, phenotypical traits of addiction (depressed mood, loss of behavioral control, compulsive drug using and concurrent psychiatric co-morbidities) have been codified. The known pathophysiology suggests neuroadaptive changes associated with dysregulation of neural circuitry in the midbrain and prefrontal area the common findings among those with substance use disorder (SUD) and to a slightly lesser degree, depression, which is not surprising considering an estimated concordance rate of 45-65 percent.
Recently, advances in neuromodulation therapy, including both deep brain stimulation and less-invasive interventions such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation has demonstrated promising effects across a wide range of neurological and neuropsychiatric disorders including depression and neurogenic pain. TMS, for example, has recently demonstrated efficacy in decreasing, at least the perception of pain, and thus reducing the need for pain medication, particularly for post-surgical patients.
Deep brain stimulation is patterned on a model of cortico-accumbal and cortico-limbic network dysfunction, as neuroimaging studies show normalization of these neural circuits after treatment (Hayes, et al, 2015). Electrical stimulation of the vmPFC was found to affect activity in the Ventral Tegmental Area (VTA) and improve depressive-like behavior. Although this research was targeting depression, the role of the vmPFC and the VTA has been well-established in the rewarding aspects SUD.
Why Does this Matter?
At present, the outcomes for patients with substance use disorder and depression are poor. Historically, patients were advised to avoid antidepressants or treatments that might trigger a relapse. But, the antidepressants themselves did not seem to clinicians to be as effective in substance use disorder + depression as they are in depression. This may be due to substances targeting the brain’s pleasure system and undermining them over time. This may also be due to the changes in brain reward threshold and induction of anhedonia in post addicts. Electrical neuromodulation appears to have some unique and promising clinical applications that may help addicts better attain and sustain recovery. In addition, the available therapies may one day allow addiction psychiatrists or interventional psychiatrists to directly target and refresh compromised neuronal circuitry in the midbrain and PFC. Certainly, more, larger and well-controlled studies are needed, but this is a promising direction for future treatment.