What Explains Mood Episodes in Bipolar Disorder?

Episodes, reward, sleep, development, and the difference between predicting change and explaining it.

Level: Intermediate
Reading load: 9 core readings in 5 units
Prerequisites: What Is a Mental Disorder? introduces diagnostic boundaries and dimensions. How Do Psychological Disorders Develop and Persist? introduces risk, temporal order, and causal explanation. How Does Depression Arise and Recur? is useful preparation for comparing depressive phases across different mood histories.
Last reviewed: September 2026

Introduction

The familiar image of bipolar disorder as a regular alternation of opposite moods conceals the questions research must answer. What defines an episode? What happens between episodes, why does change begin when it does, and why do courses differ? Changes in energy and activity, as well as depressive difficulties, require explanation in their own terms, without assuming that either is simply the reverse of the other.

This path begins with definition and observed course, then examines reward-related and sleep-related proposals. It moves from factors measured before a later episode to changes within an existing illness, before considering developmental histories, people’s accounts of living well, and an intervention aimed at recurrence. Each design supplies a different kind of evidence.

By the end, you should be able to distinguish a vulnerability from an emerging symptom or trigger, separate differences between people from changes within a person, and evaluate what a treatment result establishes about an explanation. The path is intermediate: some analyses are demanding, but the guidance introduces the distinctions needed to follow their reasoning. The goal is to assess research, not to diagnose an individual or choose treatment.

Unit 1 of 5

What is an episode, and what happens between episodes?

A study of causes first needs an outcome. Begin with the difficulty of describing mood problems across a lifetime, then examine what changes when research follows symptoms below the threshold for a major episode. Keep diagnostic subtype, current state, and long-term burden distinct.

Reading
1 of 9
Bipolar Disorder Diagnosis: Challenges and Future Directions
Phillips, M. L., & Kupfer, D. J. (2013). Bipolar disorder diagnosis: Challenges and future directions. The Lancet, 381(9878), 1663–1671. https://doi.org/10.1016/s0140-6736(13)60989-7
Critical reappraisal · Moderate · Full work: 9 pages
Compare the current presentation with the lifetime history needed to interpret it.
Why you’re reading it. Establish the descriptive problem before evaluating theories of mood episodes.
A question to consider. If two samples both report “depression,” what differences in prior activation and diagnostic definitions would you need to check before combining them?
Reading
2 of 9
The Long-Term Symptomatic Course of Bipolar I Disorder
Judd, L. L., Akiskal, H. S., Schettler, P. J., Endicott, J., Maser, J., Solomon, D. A., Leon, A. C., Rice, J. A., & Keller, M. B. (2002). The long-term natural history of the weekly symptomatic status of bipolar I disorder. Archives of General Psychiatry, 59(6), 530–537. https://doi.org/10.1001/archpsyc.59.6.530
Landmark empirical study · Moderate · Full work: 8 pages
Consider how the outcome changes when observation includes lesser symptoms.
Why you’re reading it. Make course an explicit target for explanation.
A question to consider. What would an episode-only measure miss?

Unit 2 of 5

How could reward and activation become dysregulated?

A theory becomes more informative when its components can be distinguished. Use the BAS review to separate wanting, pleasure, learning, and sustained pursuit. Then examine whether measuring a proposed vulnerability before first onset removes the main alternative explanations. The review already discusses the prospective study; returning to its original methods lets you test how well the synthesis represents the evidence.

Reading
3 of 9
The Behavioral Activation System and Mania
Johnson, S. L., Edge, M. D., Holmes, M. K., & Carver, C. S. (2012). The behavioral activation system and mania. Annual Review of Clinical Psychology, 8(1), 243–267. https://doi.org/10.1146/annurev-clinpsy-032511-143148
Major synthesis · Foundational argument · Challenging · Full work: 25 pages
Track which reward-related processes the theory needs, rather than treating “reward sensitivity” as a single observation.
Why you’re reading it. Develop a specific account of activation that can generate contrasting predictions.
A question to consider. After a success, what observations would distinguish greater pleasure from continued escalation of effort?
Reading
4 of 9
Reward Sensitivity and First Onset of Bipolar Spectrum Disorders
Alloy, L. B., Bender, R. E., Whitehouse, W. G., Wagner, C. A., Liu, R. T., Grant, D. A., Jager-Hyman, S., Molz, A., Choi, J. Y., Harmon-Jones, E., & Abramson, L. Y. (2012). High Behavioral Approach System (BAS) sensitivity, reward responsiveness, and goal-striving predict first onset of bipolar spectrum disorders: A prospective behavioral high-risk design. Journal of Abnormal Psychology, 121(2), 339–351. https://doi.org/10.1037/a0025877
Methodological contribution · Moderate · Full work: 13 pages
Follow the prospective comparison and the exact outcomes counted as first onset.
Why you’re reading it. Test the theory against a study whose predictors precede the outcome.
A question to consider. Would the observed pattern establish the theory’s account of mania if none of the first onsets were bipolar I? Specify what it supports and what still needs testing.

Unit 3 of 5

How might sleep and rhythms influence mood?

Sleep, circadian timing, and daily routines are connected but distinguishable. A framework of feedback makes their relations explicit; intensive longitudinal evidence then tests some of those relations at a particular timescale. Ask whether the measures address the proposed process and whether a group average describes each person.

Reading
5 of 9
Sleep and Circadian Rhythms in Bipolar Disorder
Harvey, A. G. (2008). Sleep and circadian rhythms in bipolar disorder: Seeking synchrony, harmony, and regulation. American Journal of Psychiatry, 165(7), 820–829. https://doi.org/10.1176/appi.ajp.2008.08010098
Foundational argument · Major synthesis · Moderate · Full work: 10 pages
Map the proposed links among sleep, circadian processes, social routines, and emotion regulation.
Why you’re reading it. Construct hypotheses that go beyond a general association between poor sleep and mood problems.
A question to consider. Which measurement would distinguish an irregular biological clock from difficulty sleeping at an otherwise stable circadian phase?
Reading
6 of 9
The Dynamic Interplay Between Sleep and Mood
Lewis, K. J. S., Tilling, K., Gordon-Smith, K., Saunders, K. E. A., Di Florio, A., Jones, L., Jones, I., O'Donovan, M. C., & Heron, J. (2023). The dynamic interplay between sleep and mood: An intensive longitudinal study of individuals with bipolar disorder. Psychological Medicine, 53(8), 3345–3354. https://doi.org/10.1017/s0033291721005377
Methodological contribution · Contemporary update · Challenging · Full work: 10 pages
Follow how the analysis separates usual levels from changes around those levels.
Why you’re reading it. Evaluate part of the feedback proposal without equating temporal prediction with proof of causation.
A question to consider. If insomnia predicts later depression but not increased activation on average, which claims from the framework remain plausible but untested by these measures?

Unit 4 of 5

How do development and context shape risk and living well?

First onset and a life with an established diagnosis are different stages of a course. Familial-risk research examines what precedes onset; lived-experience research asks how people understand wellness within relationships and everyday circumstances. Neither a predicted risk nor a reported strategy explains a whole life. Read them together to consider timing, agency, available support, and the outcomes a theory ought to address.

Reading
7 of 9
Toward the Definition of a Bipolar Prodrome
Hafeman, D. M., Merranko, J., Axelson, D., Goldstein, B. I., Goldstein, T., Monk, K., Hickey, M. B., Sakolsky, D., Diler, R., Iyengar, S., Brent, D., Kupfer, D., & Birmaher, B. (2016). Toward the definition of a bipolar prodrome: Dimensional predictors of bipolar spectrum disorders in at-risk youths. American Journal of Psychiatry, 173(7), 695–704. https://doi.org/10.1176/appi.ajp.2015.15040414
Methodological contribution · Challenging · Full work: 10 pages
Compare earlier vulnerability indicators with changes nearer to a first diagnosis.
Why you’re reading it. Distinguish a developmental predictor from an emerging manifestation of the outcome.
A question to consider. How would you test whether increasing activation is a cause of onset, an early part of the episode, or both?
Reading
8 of 9
What Works for People With Bipolar Disorder?
Suto, M., Murray, G., Hale, S., Amari, E., & Michalak, E. E. (2010). What works for people with bipolar disorder? Tips from the experts. Journal of Affective Disorders, 124(1–2), 76–84. https://doi.org/10.1016/j.jad.2009.11.004
Methodological contribution · Accessible · Full work: 9 pages
Examine how participants connect routines, relationships, and personal meaning with staying well.
Why you’re reading it. Widen the account of course beyond symptom levels while evaluating a different kind of evidence.
A question to consider. If a valued routine depends on secure housing or flexible work, what would an explanation miss by measuring only individual adherence to it?

Unit 5 of 5

What would test an explanation of recurrence?

An intervention can bring an explanatory proposal into contact with a controlled comparison. End by distinguishing the effect of a combined treatment from the contribution of its ingredients, and improvement in an acute episode from prevention afterwards. Return to the earlier models to identify the causal claim that remains unresolved.

Reading
9 of 9
Interpersonal and Social Rhythm Therapy: Two-Year Outcomes
Frank, E., Kupfer, D. J., Thase, M. E., Mallinger, A. G., Swartz, H. A., Fagiolini, A. M., Grochocinski, V., Houck, P., Scott, J., Thompson, W., & Monk, T. (2005). Two-year outcomes for interpersonal and social rhythm therapy in individuals with bipolar I disorder. Archives of General Psychiatry, 62(9), 996–1004. https://doi.org/10.1001/archpsyc.62.9.996
Landmark empirical study · Methodological contribution · Challenging · Full work: 9 pages
Distinguish the randomized comparison from the proposed mediator.
Why you’re reading it. Evaluate a test of an explanatory approach.
A question to consider. What design would separate the candidate mechanisms?

Scope and omissions

This path examines bipolar mood episodes through definition, course, reward and activation, sleep and circadian processes, development, and everyday context. It includes bipolar I, bipolar II, and research-defined spectrum outcomes, but these populations are not interchangeable. Depressive symptoms remain part of the question throughout.

It is not a diagnostic manual, an individual risk calculator, or a treatment-selection guide. It does not comprehensively cover genetics, neurochemistry, medication effects, psychosis, substance-related presentations, perinatal episodes, or later-life bipolar disorder. The biological reviews introduce hypotheses rather than a complete account of pathophysiology. Most evidence comes from North American and UK settings, often selected research samples; relationships, resources, and diagnostic meanings may differ elsewhere.

Synthesis

The broad question of what causes bipolar disorder becomes more useful as it is divided. First onset, the timing of a change, persistent symptoms, recurrence, and living well with continuing vulnerability are different outcomes. A theory may illuminate one more than another. Understanding grows when we identify that contribution precisely and resist transferring its evidence to questions it has not yet answered.

Reward-related models offer specific proposals about activation; sleep and circadian accounts connect bodily timing with behavior and circumstances. Prospective studies make temporal order clearer while leaving alternatives, and repeated measurements show why the average relationship need not describe every person. Familial risk and early symptoms identify patterns worth understanding without making later illness inevitable. People’s accounts of wellness add outcomes and contextual questions that symptom measures can miss.

An intervention can improve a course without identifying the original cause or isolating one mechanism. As a final exercise, propose an explanation for one clearly specified transition: first onset, worsening depressive symptoms, increasing activation, or recurrence. Identify its population, timescale, predicted observation, strongest available evidence, and one plausible alternative. Then design a comparison that could favor one account over the other, including an outcome meaningful to the people participating.

For the wider causal framework, return to How Do Psychological Disorders Develop and Persist?. To deepen the distinction between sleep pressure, circadian timing, and environmental cues, follow How Do Biological Rhythms Organize Sleep and Waking?. Explore other clinical questions in Psychopathology.

To examine how anticipation, learning, and interpretation can sustain difficulties, follow When Do Fear and Worry Become Persistent Problems?. It compares explanations across phobic, panic, social-anxiety, and worry research.