What The Current Research Says About Treatment-Resistant Bipolar Depression

Medically reviewed by Melissa Guarnaccia, LCSW
Updated March 28th, 2025 by BetterHelp Editorial Team
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Treatment-resistant bipolar depression (TRBD) occurs when symptoms of bipolar disorder do not respond well to typical pharmacological treatments, such as antidepressants, antipsychotics, and mood stabilizers. Current scientific research is exploring the effectiveness of alternative methods that may be effective for TRBD when the standard mechanisms are not adequately effective. While research into these new modes of treatment is relatively scarce, some treatment methods are emerging as promising. Below, learn more about these options and the symptoms of treatment-resistant bipolar disorder and depression. 

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Understanding treatment-resistant bipolar depression

Bipolar disorder (previously called “manic depression”) is characterized by mood states called hypomania, mania, and depression. Mania describes a condition of abnormally elevated energy levels that can affect mood, emotions, and activity level. 

Manic episodes only occur in bipolar I disorder and are associated with grandiosity, talkativeness, euphoria, impulsiveness, lack of sleep, and complete absorption in activities. Delusions and hallucinations may present as psychotic symptoms of a manic episode. Hypomania occurs in all types of bipolar disorder and is a less severe form of mania without psychotic features.

A major depressive episode may follow a period of mania. Symptoms of bipolar depression may include:

  • Sadness, emptiness, or hopelessness
  • A loss of interest in previously enjoyed activities 
  • Weight fluctuations
  • Sleep disturbances
  • Low energy
  • Difficulty concentrating
  • Suicidal thoughts or behaviors

Symptoms of bipolar depression are similar to those of major depressive disorder (also known as unipolar depression). However, bipolar and unipolar depression are distinct conditions.

The criteria for treatment-resistant bipolar depression include “failure to reach sustained remission or tolerate at least two different adequate treatment trials after at least eight weeks at therapeutic doses with acceptable adherence.” Mood stabilizers, antipsychotics, and other standard treatments for bipolar disorder may be used in these trials. Treatment-resistant depression may lead to prolonged depressive episodes that may become difficult to manage.

The challenges of treating TRBD

Because TRBD mimics other mood disorders, diagnosing and treating symptoms may be challenging. Symptoms such as persistent low mood, fatigue, and cognitive impairment often overlap with those of major depressive disorder (MDD), sometimes making an accurate and assured diagnosis complicated.

However, unlike MDD, which is characterized solely by depressive episodes, TRBD involves the cyclical mood swings of bipolar disorder, including manic or hypomanic episodes. Additionally, the fluctuating nature of bipolar disorder can complicate the assessment of treatment efficacy.

Individuals with treatment resistance are at an increased risk of social isolation, functional impairment, and self-harm, underscoring the need for innovative therapeutic methods and personalized approaches to improve treatment outcomes and enhance individuals’ overall well-being.

Current research on the underlying mechanisms of bipolar disorder

Treatment-resistant bipolar depression has been reported in approximately one-fourth of individuals with diagnosed bipolar disorders. Genetic and neurobiological research has shed light on some mechanisms that may cause or intensify TRBD, including the following: 

  • Genetic factors: Polygenetic risk scores and familial inheritance patterns suggest a strong genetic component of TRBD.
  • Neurobiological mechanisms: Neurotransmitter dysregulation and altered brain circuitry may contribute to mood instability.
  • Role of inflammation: Elevated cytokine levels and immune system dysfunction are associated with depressive episodes.

The likelihood of being diagnosed with treatment-resistant bipolar depression may be affected by the presence of the above risk factors, chronic stress, and the presence of comorbid conditions like anxiety disorders or a substance use disorder. Understanding these mechanisms may help scientists develop targeted therapies that are tailored to the root causes of each individual’s needs and improve their treatment response. In addition, treatments for co-occurring conditions can be developed, such as anxiety treatments that also support bipolar disorder. 

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Neurotransmitter imbalances in TRBD

Neurotransmitters like dopamine, serotonin, and norepinephrine transmit signals between nerve cells in the brain. Depressive symptoms are associated with low levels of serotonin, a pleasure hormone, which can cause low mood, lack of pleasure, and sleep disturbances. Dopamine transmission is also often dysregulated in cases of TRBD, which can cause mood instability and anhedonia, reinforcing the symptoms of low mood associated with decreased serotonin levels.

Some research supports that high concentrations of glutamate, an amino acid, may contribute to the onset of depressive symptoms by contributing to excitotoxicity and mood episodes. Homing in on the specific hormonal imbalances associated with TRBD may make way for novel treatments like ketamine and Esketamine to restore neurotransmitter function and alleviate symptoms of TRBD.

Genetic factors contributing to bipolar disorder

Like many mental health conditions, TRBD is associated with genetic risk factors. For example, having a family history of bipolar disorder increases an individual’s risk of having the disorder. The heritability of bipolar disorder is estimated to be between 79% and 93%.

However, research has identified several specific genetic markers associated with mood instability. Variations in the CACNA1C and ANK3 genes have been linked to bipolar disorder in European populations, but contradictory results have been found in other populations. Analysis of a more diverse sample population may be required to solidify the link between these genes and bipolar disorder. Further genetic testing based on specific genetic profiles can help identify which medications are most likely to be effective for individual patients with TRBD.

Innovative approaches for treating TRBD

Ketamine and Esketamine are rapid-acting NMDA receptor antagonists that may reduce symptoms of depression quickly—often within a matter of hours. While these therapies have been approved for treatment-resistant depression, they have not yet been approved for treatment-resistant bipolar depression. However, preliminary studies support that Esketamine therapy may be effective for TRBD.

Transcranial magnetic stimulation (TMS) is another novel treatment method for treatment-resistant depression that involves noninvasive brain stimulation that targets mood-regulating regions. Researchers hypothesize that TMS could be effective for TRBD, but further research is required to determine whether this lack of significant differences in outcomes is scientifically supported.

Another emerging therapy for treatment-resistant bipolar depression is psilocybin-assisted therapy. Randomized controlled trials of repeated doses of psilocybin to individuals found that psilocybin-assisted therapy was effective, safe, and tolerable to subjects with TRBD—without serious adverse events. 

The BetterHelp platform is not intended to provide any information regarding which medication or medical treatment may be appropriate for you. The content provides generalized information that is not specific to one individual. Do not take any action without consulting a qualified medical professional.

Study insights: The role of brain stimulation in reducing bipolar depression

Vagus nerve stimulation (VNS) is another emerging therapy, with one 2020 study finding that 63% of those treated with VNS in addition to standard methods had a significant reduction in depressive symptoms. However, more research is needed as this study was not a placebo-controlled trial.

Pointedly stimulating other brain regions associated with mood and cognitive function—such as the subgenual anterior cingulate cortex and nucleus accumbens—with magnetic seizure therapy and other methods may also be helpful in future TRBD approaches. Deep brain stimulation could potentially be used in cases where an individual meets multitherapy-resistant criteria for bipolar depression. However, more research into these alternative methods is necessary.

Study insights: Efficacy of lithium augmentation for bipolar disorder

A 2022 review of clinical trials and meta-analyses explored the effectiveness of lithium augmentation in individuals with TRBD. The results of the study found that lithium:

  • Improved response rates to treatments
  • Reduced relapse frequency into future manic episodes
  • Could be relatively safe and tolerable regarding side effects

The study also notes that while lithium is particularly effective in preventing the onset of future manic episodes, it is less effective in preventing depressive episodes. This study suggests that lithium treatments are best used in conjunction with other methods as part of a holistic treatment plan.

Emerging treatments for treatment-resistant bipolar depression and major depressive disorder 

Ongoing research is exploring innovative treatment solutions, including:

  • Psychedelic-assisted treatment, focusing on psilocybin and MDMA
  • Neurostimulation technologies, including transcranial direct current stimulation and closed-loop deep brain stimulation
  • Digital tools that integrate artificial intelligence to improve mental health monitoring and offer virtual support communities that enhance personalized treatment plans

Role of psychotherapy in major depressive episodes

Specific psychotherapeutic approaches may supplement prescription medications for TRBD. These include cognitive-behavioral therapy (CBT), which addresses harmful thought patterns and coping strategies, and dialectical behavior therapy (DBT), which enhances emotional regulation and distress tolerance. Therapy may become critical to improving treatment adherence and long-term outcomes of TRBD.

Addressing major depressive episodes in bipolar disorder

Research supports that a comprehensive approach to managing depressive episodes of bipolar disorder might include:

  • Mood stabilizers to prevent mood swings (talk to your doctor about the best options for you) 
  • Psychotherapy, which can enhance emotional regulation and treatment adherence
  • Lifestyle modifications, such as healthy sleeping levels, regular exercise, and nutritious eating to support overall well-being

Consulting with a licensed health practitioner is advisable when treating bipolar disorder.

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Online therapy for TRBD symptoms 

Online therapy through a platform like BetterHelp may be beneficial for individuals with TRBD who have difficulty leaving their homes due to their depressive symptoms. Digitally administered therapy allows patients to connect with a mental healthcare specialist from wherever they have secure, reliable internet access, practically eliminating geographical limitations associated with commuting to time-inflexible in-person appointments.

Certain long-term studies, like the National Institute of Mental Health (NIMH) Systematic Treatment Enhancement Program for Bipolar Disorder, work to analyze the effectiveness of a combination approach that includes pharmacological and psychosocial methods of treating bipolar disorder. This particular NIMH study found that participants who received intensive psychotherapies had a more successful recovery rate (64%) than others.

Online therapy is equally as effective in treating bipolar depression alongside lithium as its in-person counterpart, suggesting that it is a viable alternative for individuals living with TRBD. However, more research is necessary to determine its overall effectiveness for TRBD. 

Takeaway

Addressing treatment-resistant bipolar depression often involves a multifaceted approach that combines standard therapies with innovative treatments and personalized strategies. By understanding the underlying mechanisms of TRBD and leveraging emerging technologies, researchers and clinicians may improve outcomes and enhance the quality of life for individuals living with TRBD.
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