The circuit basis for chronic pain and its comorbidities

PURPOSE OF REVIEW

Chronic pain is poorly treated with many developing disabling comorbidities such as anxiety, depression and insomnia. Considerable evidence supports the idea that pain and anxiodepressive disorders share a common neurobiology and can mutually reinforce, which has significant long-term implications as the development of comorbidities leads to poorer treatment outcomes for both pain and mood disorders. This article will review recent advances in the understanding of the circuit basis for comorbidities in chronic pain.

RECENT FINDINGS

A growing number of studies have aimed to determine the mechanisms underlying chronic pain and comorbid mood disorders by using modern viral tracing tools for precise circuit manipulation with optogenetics and chemogenetics. These have revealed critical ascending and descending circuits, which advance the understanding of the interconnected pathways that modulate the sensory dimension of pain and the long-term emotional consequences of chronic pain.

SUMMARY

Comorbid pain and mood disorders can produce circuit-specific maladaptive plasticity; however, several translational issues require addressing to maximise future therapeutic potential. These include the validity of preclinical models, the translatability of endpoints and expanding analysis to the molecular and system levels.

Comorbid Premenstrual Dysphoric Disorder in Women with Bipolar Disorder: Management Challenges

Bipolar disorder (BD) and premenstrual dysphoric disorder (PMDD) are two cyclic mood illnesses, sometimes presenting together. Their comorbidity appears to be linked to common biological mechanisms and usually results in more severity of mood symptoms and a poorer long-term outcome. Nevertheless, the management of comorbid PMDD/BD has been scarcely studied. Therefore, the aim of the present paper was to review the published literature on the treatment of comorbid PMDD/BD and to provide point-by-point hypotheses to address these complex clinical cases. We searched PubMed to identify the studies focused on the treatment and management of comorbid PMDD/BD using the following search words, alone and in combination: premenstrual dysphoric disorder, bipolar disorder, comorbid, treatment, management, pharmacotherapy, psychotherapy. The search was conducted on the 1st of June 2019 and yielded 55 records. Four papers met our inclusion/exclusion criteria and were therefore included in our qualitative synthesis. Integrating the few data pertaining to the treatment of comorbid PMDD/BD with the large amount of published data on the two conditions separately, we can suggest that the management of comorbid PMDD/BD needs as a first step to stabilize the bipolar symptoms by means of optimal dosages of mood stabilizers. Then, in euthymic BD patients, the PMDD symptoms could be treated with estroprogestins (first-line treatment). On the contrary, during acute phases of BD, antidepressants (for major depressive episodes) and atypical antipsychotics/hormonal modulators (for manic episodes) could be considered as promising add-on treatments to mood stabilizers. In case of resistant PMDD/BD symptoms, combined strategies should be taken into account, as well as alternative treatments, such as lifestyle changes. In conclusion, RCTs on comorbid PMDD/BD are still lacking. The management of this complex condition is therefore challenging and it requires a tailored treatment.