Patients with bipolar disorder (BD) have a wide range of neurocognitive dysfunction, which lead to impaired psychosocial function and reduced quality of life. Therefore, improving neurocognitive function has become an important goal of BD treatment. Aiming at this, some clinical studies have been performed but failed to illustrate significant positive efficacies of pharmacological therapy or non-pharmacological therapy, which could attribute in part to insufficient understanding on the risk factors that affect the neurocognitive function of BD patients. Delayed diagnosis of BD is so common that a lot of patients receive long-term antidepressant treatment before of diagnosis of unipolar depression. There is controversy about whether antidepressant treatment in early stage would affect the neurocognitive function of BD patients. In view of the high prevalence of delayed diagnosis and the use of antidepressants, it is of great scientific significance and clinical value to clarify this matter and other factors that may potentially affect the neurocognitive function of BD patients.

Subjects will not be engaged with any interventions in this study. Two senior psychiatrists are in attendance of screening the patients with the inclusion/exclusion criteria, and then all patients who meet both criteria and are willing to participate in this study will sign the informed consent before enrollment. The participants will be divided into AT or NT group according to their history of antidepressant treatment in early stage, which is done by the two senior psychiatrists. Then these senior psychiatrists will also collect additional study parameters, such as age, sex, nation, age of onset, and score of Premorbid Adjustment Scale (PAS). Furthermore, the information about history of treatments and diagnosis will be further confirmed with medical documentary and patients' guardians. Afterwards, other investigators will finish the rating work of the rest of scales. The whole procedure should be done within 180 min. Finally, ten milliliters of venous blood are adopted for measuring NSE

Inclusion Criteria:

1. A diagnosis of BD diagnosed according to the Diagnostic and Statistical Manual of Mental disorders, Fourth Edition (DSM-IV-TR) diagnosed with Structured Clinical Interview for DSM-IV (SCID); a current state of euthymia is defined by both scores of Montgomery-Åsberg Depression Scale (MADRS) and Young Manic Rating Scale (YMRS) <7, lasting for 4 weeks at least before recruitment
2. Initiated with a depressive episode
3. Aged between 18~50 years
4. Patients comply with all procedures of study
5. Participants must sign the informed consent

Exclusion Criteria:

1. A history of psychiatric symptoms
2. A comorbidity of attention deficit and hyperactivity disorder (ADHD)
3. Neurological trauma or neurological diseases which could cause cognition injury
4. History of substance dependence/abuse
5. Received modified electroconvulsive therapy (MECT) in the past 12 months
6. Severe physical disease affecting cognitive function or increasing peripheral NSE
7. Recent drug use that affects cognition, such as tricyclic antidepressants, anticholinergic drugs, amphetamines, etc.
8. IQ <70
9. Use benzodiazepines 4 hours before scale evaluation

This study will consist of a sample of 124 patients with bipolar disorder who initiated with a depressive episode and being a euthymic state for 4 weeks at least before enrollment.All participants are divided into two groups according to whether they had received systemic antidepressant treatment or not in the early stage.

Request based on researcher's consent

the data will be available openly after the study finished with no termination.