Bipolar disorder (BD) is a chronic and severe psychiatric disease. There are often significant delays prior to diagnosis, and only 30 to 40 % of patients will experience complete remission. Since BD occurs most often at a young age, the disorder can seriously obstruct future socio-professional development and integration. Vulnerability-stress model of BD is considered to be the result of an interaction between vulnerability genes and environmental risk factors, which leads to the onset of the disorder most often in late adolescence or early adulthood. The clinical "staging" model of BD situates the subject in a clinical continuum of varying degrees of severity (at-risk status, first episode, full-blown BD). Given the demonstrated effectiveness of early intervention in the early stages of psychotic disorder, we posit that early intervention for early stages of BD (i.e. at-risk status and first episode mania or hypomania) would reduce the duration of untreated illness and optimize the chances of therapeutic response and recovery.
We conducted a narrative review of the literature to gather updated data on: (1) features of early stages: risk factors, at-risk symptoms, clinical specificities of the first manic episode; (2) early screening: targeted populations and psychometric tools; (3) early treatment: settings and therapeutic approaches for the early stages of BD.
(1) Features of early stages: among genetic risk factors, we highlighted the diagnosis of BD in relatives and affective temperament including as cyclothymic, depressive, anxious and dysphoric. Regarding prenatal environmental risk, we identified peripartum factors such as maternal stress, smoking and viral infections, prematurity and cesarean delivery. Later in the neurodevelopmental course, stressful events and child psychiatric disorders are recognized as increasing the risk of developing BD in adolescence. At-risk symptoms could be classified as "distal" with early but aspecific expressions including anxiety, depression, sleep disturbance, decreased cognitive performance, and more specific "proximal" symptoms which correspond to subsyndromic hypomanic symptoms that increase in intensity as the first episode of BD approaches. Specific clinical expressions have been described to assess the risk of BD in individuals with depression. Irritability, mixed and psychotic features are often observed in the first manic episode. (2) Early screening: some individuals with higher risk need special attention for screening, such as children of people with BD. Indeed, it is shown that children with at least one parent with BD have around 50 % risk of developing BD during adolescence or early adulthood. Groups of individuals presenting other risk factors, experiencing an early stage of psychosis or depressive disorders should also be considered as targeted populations for BD screening. Three questionnaires have been validated to screen for the presence of at-risk symptoms of BD: the Hypomanic Personality Scale, the Child Behavior Checklist-Paediatric Bipolar Disorder, and the General Behavior Inventory. In parallel, ultra-high risk criteria for bipolar affective disorder ("bipolar at-risk") distinguishing three categories of at-risk states for BD have been developed. (3) Early treatment: clinical overlap between first psychotic and manic episode and the various trajectories of the at-risk status have led early intervention services (EIS) for psychosis to reach out for people with an early stage of BD. EIS offers complete biopsychosocial evaluations involving a psychiatric examination, semi-structured interviews, neuropsychological assessments and complementary biological and neuroimaging investigations. Key components of EIS are a youth-friendly approach, specialized and intensive care and client-centered case management model. Pharmaceutical treatments for at-risk individuals are essentially symptomatic, while guidelines recommend the use of a non-antipsychotic mood stabilizer as first-line monotherapy for the first manic or hypomanic episode. Non-pharmacological approaches including psychoeducation, psychotherapy and rehabilitation have proven efficacy and should be considered for both at-risk and first episode of BD.
EIS for psychosis might consider developing and implementing screening and treatment approaches for individuals experiencing an early stage of BD. Several opportunities for progress on early intervention in the early stages of BD can be drawn. Training first-line practitioners to identify at-risk subjects would be relevant to optimize screening of this population. Biomarkers including functional and structural imaging measures of specific cortical regions and inflammation proteins including IL-6 rates constitute promising leads for predicting the risk of transition to full-blown BD. From a therapeutic perspective, the use of neuroprotective agents such as folic acid has shown particularly encouraging results in delaying the emergence of BD. Large-scale studies and long-term follow-up are still needed to achieve consensus in the use of screening and treatment tools. The development of specific recommendations for the early stages of BD is warranted.