Bipolar and Depression Shared Risk and Your Genetics

By the ExomeDNA Research Team | Last reviewed May 2026

This page contains general information only. For personal health decisions, consult a qualified clinician.

Bipolar and Depression Shared Risk reflects a well-characterized pattern in psychiatric genetics: bipolar disorder (BPD) and major depressive disorder (MDD) share a meaningful portion of their genetic architecture, meaning variants that elevate susceptibility to one condition often confer overlapping risk for the other. Large-scale genome-wide association analyses have identified common variants near genes including ANK3 and CACNA1C that contribute to this shared landscape, with the ANK3 locus — encoding the neuronal scaffolding protein ankyrin-G — among the most replicated findings across multiple independent BPD and cross-disorder GWAS datasets (Liu et al., 2011; Coleman et al., 2020). Below: what the genetics means, which genes and pathways are involved, and how this information can support informed conversations with a clinician.

What is bipolar and depression shared risk?

Bipolar disorder and major depressive disorder are distinct clinical categories, yet psychiatric genetics has long recognized that the two conditions do not occupy entirely separate biological territory. Both involve dysregulation of mood, energy, and cognition. Both respond to overlapping classes of medication. And both, it turns out, are influenced by many of the same common genetic variants.

The concept of shared genetic risk — sometimes called cross-disorder or trans-condition genetic liability — does not mean a person carries a single gene "for" either condition. Rather, it reflects the fact that hundreds of common variants, each with a small individual effect, collectively shape neurobiological pathways that matter to mood regulation broadly. When GWAS studies examine both conditions in tandem, they consistently find significant overlap in the associated loci. A landmark meta-analysis examining both BPD and MDD discovered that the strongest genetic signals cluster in genomic regions tied to neuronal excitability, calcium signaling, and cytoskeletal organization — biological themes that cut across the mood spectrum rather than discriminating cleanly between mania and depression (Liu et al., 2011).

This cross-disorder framing matters for how the result is interpreted. A higher polygenic signal in this trait space does not mean certainty of developing either condition — the vast majority of individuals with elevated genetic loading never develop bipolar disorder or major depressive disorder. It reflects probabilistic susceptibility at the population level, shaped substantially by environment, life history, and factors that genetics alone cannot capture.

The genetics behind bipolar and depression shared risk

Several genes have emerged as consistent contributors to the shared genetic architecture of BPD and MDD. Among these, ANK3 stands out as one of the most replicated and mechanistically informative findings in the BPD GWAS literature.

ANK3 — the axon initial segment gene

ANK3 encodes ankyrin-G, a large scaffolding protein whose most critical function in neurons occurs at a specialized structure called the axon initial segment (AIS). The AIS is the narrow region at the base of a neuron's axon where action potentials are initiated — it is, in a literal sense, the trigger point for all neuronal firing. Ankyrin-G organizes the molecular machinery of this decision: it clusters voltage-gated sodium channels (Nav1.1, Nav1.2, Nav1.6), Kv7 potassium channels, and the cell-adhesion molecules that define the AIS as a specialized excitability hub. When ANK3 function is altered, the composition and density of these ion channels at the AIS shifts, which changes the threshold at which a neuron fires.

This biology maps onto the phenomenology of mood episodes in bipolar disorder. Manic episodes are characterized by neuronal hyperexcitability — racing thoughts, reduced need for sleep, pressured speech — while depressive episodes involve a state of hypoexcitability and reduced drive. ANK3 variants that alter AIS organization may shift the excitability set-point that determines how readily a neuron transitions between these states. Ankyrin-G also organizes inhibitory synapses, where it clusters GABA-A receptors; disrupted inhibitory tone compounds the excitability dysregulation. The variant rs10994397 near ANK3 is among the most well-replicated signals in bipolar disorder GWAS, and its presence in cross-disorder datasets underscores that this axonal mechanism contributes broadly to mood disorder susceptibility rather than to mania alone.

CACNA1C — calcium amplification of neuronal activity

CACNA1C encodes the alpha-1C subunit of the L-type voltage-gated calcium channel (Cav1.2). L-type calcium channels open in response to membrane depolarization and allow calcium to flow into the cell. In neurons, this calcium entry activates downstream transcription factors — including CREB and NFAT — that regulate which genes are expressed in response to activity. Cav1.2 channel variants that alter channel density or kinetics therefore change how strongly neurons translate electrical activity into lasting gene expression changes. This is directly relevant to mood state: the sustained low activation and reduced reward response of major depression, and the heightened reactivity and reward hypersensitivity of mania, both involve changes in how neurons respond to stimulation over time. ANK3 and CACNA1C signals have been co-detected in multiple large datasets examining the shared BPD-MDD landscape (Coleman et al., 2020).

ASTN2 — neuronal migration and pleiotropic risk

ASTN2 encodes astrotactin-2, a membrane glycoprotein required for the glia-guided migration of neurons during brain development. ASTN2 has emerged as a pleiotropic signal across multiple neuropsychiatric phenotypes, appearing in association studies for autism, schizophrenia, bipolar disorder, and depression. Its role in establishing the precise laminar positioning of neurons during development may contribute to the circuit-level differences observed across these conditions. In the cross-disorder BPD-MDD context, ASTN2 represents a developmental signal that may influence the structural substrate on which excitability dysregulation later operates.

ACADS — mitochondrial energy in neurons

ACADS encodes short-chain acyl-CoA dehydrogenase, a mitochondrial enzyme that catalyzes the first step in the beta-oxidation of short-chain fatty acids. While this may seem distant from mood regulation, mitochondrial energy metabolism has been proposed as a contributing factor in bipolar disorder pathophysiology: neurons in mood-relevant circuits have high energy demands, and subtle inefficiencies in mitochondrial function may make these circuits more vulnerable to the kind of dysregulation observed across mood episodes. ACADS variants may affect mitochondrial energy production efficiency in neurons, adding a metabolic dimension to the multi-pathway architecture of this shared risk trait.

What the research says

Research base: Moderate. The shared genetic architecture of bipolar disorder and major depressive disorder is supported by multiple large-scale genome-wide association studies, though the precise variant-level mechanisms remain an area of ongoing investigation.

A foundational meta-analysis of GWAS data examining both bipolar disorder and major depressive disorder simultaneously identified common genetic signals that span both conditions, with neuronal excitability and ion channel pathways among the most consistently implicated biological themes (Liu et al., 2011). This cross-disorder approach was deliberately designed to detect variants whose effects are not confined to a single condition — variants that contribute to mood instability broadly.

A subsequent large-scale genomic analysis of the mood disorder spectrum examined the genetic architecture across BPD, MDD, and related phenotypes, identifying additional loci and confirming the substantial genetic correlation between the two conditions (Coleman et al., 2020). This work reinforces that from a genomic standpoint, bipolar disorder and major depressive disorder exist on a continuum of shared molecular susceptibility rather than as categorically distinct biological entities.

Key observations from this body of research:

• The ANK3 locus is among the most replicated signals in bipolar disorder GWAS, and its detection in cross-disorder analyses confirms its relevance to the shared BPD-MDD risk landscape (Liu et al., 2011).
• CACNA1C variants appear across multiple independent BPD and mood spectrum datasets, reflecting the central role of calcium signaling in neuronal activity regulation (Coleman et al., 2020).
• Genetic correlation analyses indicate meaningful overlap between the genetic architectures of BPD and MDD, supporting the biological validity of examining them together.
• The implicated pathways — axonal excitability organization, L-type calcium channel function, neuronal migration, and mitochondrial energy metabolism — converge on the biology of how neurons fire, adapt, and maintain stable states of activity.

It is important to note that common variant genetic studies of this kind identify population-level associations. Any individual's clinical trajectory is shaped by many factors beyond the variants captured in these analyses.

How bipolar and depression shared risk affects you

A result in this trait reflects the aggregate signal from common variants associated with the shared genetic risk landscape spanning bipolar disorder and major depressive disorder. This signal operates at the level of neurobiological pathways — particularly those governing how neurons set and maintain their excitability thresholds, how calcium entry regulates activity-dependent gene expression, and how neuronal circuits develop and sustain stable states.

For most individuals, this kind of polygenic signal is one input among many that shape lifetime mental health. Mood disorders are highly treatable conditions: effective medications exist for both major depressive disorder (including SSRIs, SNRIs, and other classes) and bipolar disorder (including mood stabilizers such as lithium and valproate, and atypical antipsychotics). Psychotherapy, particularly cognitive behavioral therapy and interpersonal therapy, has well-established efficacy across the mood spectrum. Genetic susceptibility does not predetermine outcomes or severity, and early engagement with mental health support is associated with better outcomes when symptoms do emerge.

Working with your bipolar and depression shared risk result

If this result is relevant to your health conversations, the following evidence-informed practices are associated with mood stability and general mental health resilience:

1. Prioritize sleep consistency. Sleep disruption is the most well-established behavioral trigger for mood episodes across the bipolar spectrum. Maintaining regular sleep and wake times — even on weekends — supports circadian rhythm stability and is a first-line behavioral strategy in bipolar disorder management.
2. Track mood patterns over time. Keeping a simple log of mood, energy, and sleep quality can help identify early warning signs of mood shifts and provide useful data for clinicians. Apps and paper mood charts are both effective.
3. Minimize cannabis and alcohol. Both substances disrupt sleep architecture and mood regulation. Cannabis in particular has documented associations with destabilizing mood episodes in individuals with bipolar susceptibility; it is best avoided or discussed explicitly with a clinician.
4. Engage early if symptoms emerge. The mood disorders have strong early-intervention evidence: the sooner treatment is initiated after a first significant episode, the better the long-term trajectory tends to be. Sharing genetic findings with a psychiatrist or primary care provider can open this conversation.
5. Support consistent medication adherence if prescribed. For individuals who are on treatment, medication adherence is the single strongest predictor of stability. Abrupt discontinuation is a well-documented trigger for relapse.
6. Discuss this result with a mental health professional. A clinician familiar with mood disorders can interpret this result in the full context of personal and family history, current symptoms, and risk factors — and can recommend monitoring, therapy, or evaluation if warranted.

Related traits and genes

Genetic susceptibility to mood disorders is one facet of a broader landscape of brain and mental health traits. Related areas of interest include:

• Bipolar Disorder Risk: ANK3 CACNA1C Genetics — focused analysis of ANK3 and CACNA1C in bipolar disorder specifically
• Mood Disorder Risk: Genetics and Brain Signaling — shared mood disorder genetic architecture
• Depression Risk: DRD2 and Genetic Factors — dopaminergic pathways and major depressive disorder risk
• Depression Severity Genetics: ANO3, ARL5B and Key Loci — genetic signals associated with depression severity variation
• Anxiety Disorder Genetics: CELF4 and Brain Circuits — shared anxiety and mood susceptibility signals

The ANK3 gene, central to this trait, appears across multiple mood and neuropsychiatric analyses. The CACNA1C gene is discussed in the context of both bipolar disorder and shared neuropsychiatric risk on the CACNA1C gene page.

Frequently asked questions

Does a higher result mean I will develop bipolar disorder or depression?

No. This result reflects a polygenic signal — the aggregate effect of many common variants — associated with population-level patterns of shared susceptibility across bipolar disorder and major depressive disorder. Most individuals with elevated genetic signals in this space do not develop either condition. Many additional factors, including environment, life experience, stress, and individual neurobiological differences, shape whether and how any genetic susceptibility is expressed.

What is the connection between bipolar disorder and major depressive disorder genetically?

Large-scale genomic studies have shown that bipolar disorder and major depressive disorder share a significant proportion of their genetic architecture. Variants near genes including ANK3 and CACNA1C appear in GWAS analyses of both conditions, reflecting the fact that the neurobiological pathways underlying mood regulation are partially shared across the condition boundary (Liu et al., 2011; Coleman et al., 2020). This does not mean the two conditions are identical — they have distinct clinical features — but they overlap meaningfully at the molecular level.

What does ANK3 do and why is it relevant to mood disorders?

ANK3 encodes ankyrin-G, a scaffolding protein that organizes the axon initial segment — the region of a neuron where action potentials begin. By clustering sodium and potassium channels at this site, ankyrin-G sets the threshold at which a neuron fires. Variants that alter ANK3 function may shift neuronal excitability set-points in mood-relevant circuits, which maps onto the pathological excitability shifts seen in manic and depressive episodes. The ANK3 locus is among the most replicated findings in bipolar disorder genetic research.

Is there anything I can do to reduce my risk given this genetic signal?

Mood disorders are influenced by many factors beyond genetics, and several behavioral patterns are associated with mood stability. Maintaining consistent sleep schedules, avoiding cannabis and excessive alcohol, tracking mood early, and engaging promptly with mental health care if symptoms arise are all evidence-supported approaches. These actions are beneficial regardless of genetic result, but they carry particular relevance for individuals with a personal or family history of mood episodes.

If I already have a confirmed condition, what does this result add?

For someone living with bipolar disorder or major depressive disorder, this result provides context about the genetic underpinnings of their condition. It does not change treatment decisions directly — those should be made with a qualified clinician — but it may reinforce the biological basis of mood episodes and support conversations about treatment options, medication adherence, and early intervention strategies.

How is this trait different from general depression risk or schizophrenia risk?

This specific GWAS trait focuses on variants associated with susceptibility spanning both bipolar disorder and major depressive disorder — a shared mood spectrum signal. It does not include schizophrenia in its primary signal. Separate ExomeDNA traits address pure bipolar disorder risk, depression-specific signals, and psychotic spectrum risk with distinct genetic architectures and featured genes.

References

1. Liu Y et al. (2011). Meta-analysis of genome-wide association data of bipolar disorder and major depressive disorder. World Journal of Biological Psychiatry, 12(5), 372-380. PMID: 20351715.
2. Coleman JRI et al. (2020). The Genetics of the Mood Disorder Spectrum: Genome-wide Association Analyses of More Than 185,000 Cases and 439,000 Controls. Biological Psychiatry, 88(2), 169-184. PMID: 31926635.

Data sources: GWAS Catalog, Open Targets Genetics (L2G gene prioritization), NCBI Gene, ClinVar, dbSNP.

ExomeDNA genetic results are for wellness and educational purposes only. Consult a clinician for personalized health guidance.