As an integrative psychiatrist, my work involves recognizing patterns in the individuals I care for, especially when their symptoms don't fully align with standard psychiatric diagnoses. During my four years of psychiatry residency, I was trained to identify and diagnose primary psychiatric conditions such as major depressive disorder, bipolar disorder, premenstrual dysphoric disorder (PMDD), borderline personality disorder, and post-traumatic stress disorder (PTSD)—all of which can involve mood dysregulation and mood swings. Treatment approaches typically focus on medications and/or psychotherapy to help manage mood instability.
However, I've become increasingly curious: What if we're missing other contributors to mood dysregulation and mood swings that extend beyond the DSM-5 criteria? Human health is complex, and underlying factors may be driving or co-occurring with primary psychiatric conditions.
This is why a detailed health history, a comprehensive timeline of physical and mental health symptoms, and appropriate lab testing are essential components of my practice. Since identifying root causes requires more time and attention, initial functional psychiatry appointments are typically longer than the standard one-hour intake.
While integrative psychiatry can still incorporate conventional treatments like medications, many of the individuals I see haven't experienced sufficient relief from psychiatric medications alone and continue to struggle with persistent mental health and physical symptoms. This is when exploring other potential contributors to mood swings becomes essential.
Candida Overgrowth
Candida albicans is a yeast commonly found in the human gastrointestinal (GI) tract. However, when it overgrows, it can lead to fungal dysbiosis—an imbalance of fungal species in the gut that disrupts human health.
Candida overgrowth has been linked to chronic inflammation and increased gut permeability (leaky gut). When the gut barrier is compromised, larger molecules such as undigested food particles, toxins, and pathogens can enter the bloodstream, triggering immune activation and the release of inflammatory cytokines. These cytokines can cross the blood-brain barrier (BBB), contributing to neuroinflammation and symptoms like anxiety, brain fog, and mood swings.
An important paper just came out last week that continues to explore the connection between gut health and neuropsychiatric symptoms, including the link between Candida overgrowth and mood instability (Hadrich, 2025).
Clinical Pearls for Candida Overgrowth:
Limiting sugar intake is key for managing Candida overgrowth since Candida thrives on sugar.
Saccharomyces boulardii, a beneficial yeast, can help reduce Candida overgrowth and support gut barrier repair (Hadrich, 2025).
Mast Cell Activation Syndrome (MCAS)
Mast Cell Activation Syndrome (MCAS) is an often overlooked immunological condition where mast cells, key players in the immune system, become hyperreactive and release excessive inflammatory chemicals such as histamine. While mast cells normally help defend against threats, in MCAS, they can overreact to everyday stimuli, leading to widespread inflammation and symptoms, including mood swings.
MCAS can drive mood instability by triggering neuroinflammation, contributing to symptoms such as anxiety, panic attacks, and unpredictable mood shifts. These mood-related issues often occur alongside physical symptoms like chronic pain, fatigue, and sensory sensitivities, making it difficult to distinguish from primary psychiatric conditions like bipolar disorder, unipolar depression, PTSD, or borderline personality disorder.
Women with MCAS frequently report symptom flares that align with hormonal changes during their menstrual cycle, suggesting a link between mast cells and hormonal fluctuations.
Clinical Pearls for MCAS:
When mood swings worsen before menstruation, consider underlying contributors like MCAS and Candida overgrowth.
Identifying MCAS can shift treatment focus to immune regulation and mast cell stabilization, rather than relying solely on psychiatric medications.
Trialing a low-histamine or low-salicylate diet can be beneficial for some individuals.
The scratch test for dermatographism (lightly stroking the skin to check for exaggerated red, raised wheals) can be a quick screening tool for MCAS.
Tickborne Diseases
Tickborne diseases, including Lyme disease, Babesiosis, and Bartonella, are increasingly recognized for their potential to cause complex neuropsychiatric symptoms, yet they are frequently overlooked in conventional mental health assessments. These infections can contribute to mood swings, cognitive changes, and emotional instability through mechanisms like chronic inflammation, immune system dysregulation, and direct effects on the nervous system.
Tickborne diseases should be considered when mood swings are accompanied by neurological, physical, and systemic symptoms, especially when symptoms present in unpredictable patterns or lack a clear situational trigger. This is particularly relevant in regions like the Upper Midwest, where tick exposure is common.
Clinical Pearls for Tickborne Diseases:
Diagnosing tickborne infections requires specialized knowledge, and referrals to practitioners with experience in tickborne disease management may be necessary.
Neuropsychiatric symptoms often emerge in later stages of infection, making early diagnosis challenging.
In some cases, psychiatric medications may be ineffective or worsen agitation, particularly selective serotonin reuptake inhibitors (SSRIs).
Mood swings and mood dysregulation are often more complex than they appear. While conventional psychiatric diagnoses provide a helpful framework, they don't always capture the full picture. Exploring potential root causes like Candida overgrowth, MCAS, and tickborne infections can lead to more effective, personalized treatment strategies.
A kind reminder: This blog post is designed as a general guide. This is not a substitute for personalized medical advice, nor is a patient-physician relationship established in this blog post.
Sources:
Bransfield, R. C., Mao, C., & Greenberg, R. (2024). Microbes and Mental Illness: Past, Present, and Future. Healthcare, 12(1), 83. https://doi.org/10.3390/healthcare12010083
Delaney, S.L., Murray, L.A., Fallon, B.A. (2022). Neuropsychiatric Symptoms and Tick-Borne Diseases. In: Savitz, J., Yolken, R.H. (eds) Microorganisms and Mental Health. Current Topics in Behavioral Neurosciences, vol 61. Springer, Cham. https://doi.org/10.1007/7854_2022_406
Hadrich, et al. (2025). Gut mycobiome and neuropsychiatric disorders: insights and therapeutic potential. Front. Cell. Neurosci. https://www.frontiersin.org/journals/cellular-neuroscience/articles/10.3389/fncel.2024.1495224/full
Voss, R. and Zhou, M. (2022). Improvement in Neuropsychiatric Symptoms With the Addition of Nortriptyline in the Context of Mast Cell Activation Syndrome. American Journal of Psychiatry Residents' Journal. https://psychiatryonline.org/doi/full/10.1176/appi.ajp-rj.2022.180206
Weinstock LB, Nelson RM, Blitshteyn S. (2023). Neuropsychiatric Manifestations of Mast Cell Activation Syndrome and Response to Mast-Cell-Directed Treatment: A Case Series. J Pers Med. https://pmc.ncbi.nlm.nih.gov/articles/PMC10672129/