Inclusion Criteria:
All participants:
* 18-40 years of age
* Not following a ketogenic diet
BD hypomanic group (n=30):
* Meeting sex proportion: 50% female
* Meeting diagnosis proportion: 50:50% Bipolar I: Bipolar II (BDI:II) (Diagnostic and Statistical Manual of Mental Disorders 5; DSM-5)
* Score greater than 10 on the Young Mania Rating Scale score(YMRS)
* BD medications will be allowed as in our previous studies: any combination of atypical antipsychotics, lithium, antidepressants, anxiolytics (common in BD)
BD euthymic group (n=30):
* Meeting sex proportion: 50% female
* Meeting diagnosis proportion: 50:50% BDI:II (DSM-5)
* Score less than or equal to 10 on YMRS
* BD medications will be allowed as in our previous studies: any combination of atypical antipsychotics, lithium, antidepressants, anxiolytics (common in BD)
Healthy Control (HC) Group (n=30):
* Sex matched with BD groups
* No psychiatric history
Exclusion Criteria:
All participants:
* Not between 18-40 years of age
* History of head injury, neurological, pervasive developmental disorder (e.g. autism), systemic medical disease and treatment (medical records, participant report)
* Mini-Mental State Examination score (cognitive state) \<24
* Premorbid National Adult Reading Test Intelligent Quotient (NAART IQ) estimate\<85
* Visual disturbance: \<20/40 Snellen visual acuity
* History of alcohol/substance use disorder (SUD; all substances, including nicotine), and/or illicit substance use (except cannabis) over the last 6 months (SCID-5). Note: lifetime/present cannabis use (at non-abuse (\<3 times in the past month) and non SUD levels) will be allowed, given its common usage in BD and young adults. Cannabis SUD over the last 6 months will not be allowed. Urine tests on scan days will exclude current illicit substance use (except cannabis). Salivary alcohol tests on scan days will exclude intoxicated individuals
* MRI exclusion: metallic objects, e.g., surgical implants; claustrophobia; positive pregnancy test for females or self-report pregnancy
* Unable to understand English
* Conditions related to the pancreas, liver, thyroid or gallbladder.
* Taking anticoagulants and/or those with blood dyscrasias (illnesses) who have coagulation disorders (eg, hemophilia) because of the ketomojo finger stick blood tests
* Scoring 3 or higher on positive symptom factor questions on the Positive and Negative Syndrome Scale (PANSS) questionnaire (indicative of psychotic symptoms)
* Currently following a ketogenic diet
* Head circumference larger than 24 inches (62cm) and/or chest circumference larger than 55 inches (139 cm)
BD hypomanic group:
* Must be meeting sex proportions: not 50% female
* Must be meeting diagnosis proportions: not 50:50% BDI:II (DSM-5)
* Diagnosis of BD in a manic or euthymic episode
* Score 10 or lower on the Young Mania Rating Scale score(YMRS)
* Using psychotropic medications other than those allowed in inclusion criteria
* Does not have a smartphone with a) iOS version 12.0 or above, or b) Android version 8 and later to use with the Keto-Mojo app
BD euthymic group:
* Not meeting sex proportion: not 50% female
* Not meeting diagnosis proportion: not 50:50% BDI:II
* Diagnosis of BD in a depressive, hypomanic, or manic episode
* Score greater than 10 on YMRS
* Using psychotropic medications other than those allowed in inclusion criteria
* Does not have a smartphone with a) iOS version 12.0 or above, or b) Android version 8 and later to use with the Keto-Mojo app
Healthy Control (HC) Group
* Not sex-matched with BD groups
* Has psychiatric history
