immediately following childbirth). There is some evidence connecting PPP with changes to levels of peripheral immune cells (e.g., lymphocytes and NK or natural killer cells) traveling in the bloodstream, but more research is required to identify the specific mechanisms and cell types involved which might be related to PPP onset. No direct evidence has shown a link between cytokine levels and PPP. Sleep Disturbance The link between sleep difficulty and PPP is not strongly supported by current evidence; however, some studies have demonstrated an increased risk for postpartum psychosis in women with bipolar disorder who have had manic episodes triggered by sleep disturbance. Diagnosis and Screening Diagnosis Not recognized as its own distinct disorder, PPP is instead classified by the DSM-V as a "Brief Psychotic Disorder with peripartum onset." Clinical requirements for the diagnosis of a brief psychotic disorder require the presence of at least one of the following psychotic symptoms: delusions, hallucinations, disorganized speech, and/or grossly disorganized or catatonic behavior. Additional requirements include that the psychotic symptom lasts between one day and one month, eventually resulting in the person recovering their previous level of functional ability, and that the symptoms are not better related to a different psychiatric illness (including the result of ingesting substances such as alcohol or drugs). The specifier, "with peripartum onset," requires the development of the above within 4 weeks of delivering a child. There are no laboratory or imaging tools available to diagnose PPP, though a work-up of different laboratory analyses and imaging of the brain may be conducted to ensure other potential confounding diagnoses (e.g., vascular disorders, infective delirium, etc.) are not the cause of the patient's presentation (see Differential, Other non-organic postpartum psychoses, and Organic postpartum psychoses). These may include, but are not limited to, a complete blood count, comprehensive metabolic panel, urinalysis and urine drug screen, and tests for thyroid functioning; further workup in the setting of classically neurological symptoms (such as delirium-like confusion) may include magnetic resonance imaging (MRI), a test of cerebrospinal fluid (CSF), or electroencephalogram (EEG). Screening Currently, no screening tools exist to evaluate for PPP, though providers may choose to use standard screens for postpartum depression and mania to evaluate the presence of these particular symptoms. Due to the presence of several symptoms that are classically associated with other postpartum conditions, such as postpartum blues or depression, and often benign changes that accompany new parenthood (anxiety, irritability,