This study aims to use a retrospective cohort approach to explore the impact of lithium carbonate on suicide and self-harm related events among adolescents and young adults with bipolar disorder in China.The primary objective of this study is to investigate the effects of lithium carbonate on suicidal ideation in adolescents and young adults with bipolar disorder in China. Secondary objectives include exploring its effects on preventing suicide attempts, non-suicidal self-injury, and aggressive behaviors in this population.

Inclusion Criteria:

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1 For Lithium group

1. Aged 12-45 years (adolescents 12-17, young adults 18-45).
2. Diagnosed with bipolar disorder using the the Mini-International Neuropsychiatric Interview (M.I.N.I.) (M.I.N.I.; version 5.0) based on Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria.
3. Adolescents diagnosed using the M.I.N.I. Kid version.
4. Lithium medication adherence of at least 80% in the first six months over the past year.
5. Not in an acute phase of illness.
6. Patient or guardian able to participate in assessment interviews.
7. Informed consent signed by participants and guardians (for adolescents).

2 for Non-lithium group

1. Aged 12-45 years (adolescents 12-17, young adults 18-45).
2. Diagnosed with bipolar disorder using the Mini-International Neuropsychiatric Interview (M.I.N.I.; version 5.0) based on DSM-IV criteria.
3. Adolescents diagnosed using the M.I.N.I. Kid version.
4. No lithium use over the past year.
5. Not in an acute phase of illness.
6. Patient or guardian able to participate in assessment interviews.
7. Informed consent signed by participants and guardians (for adolescents).

Exclusion Criteria:

1. Severe physical illness or active substance abuse.
2. Severe cognitive impairments, including developmental delays or dementia.

Individuals with bipolar disorder ranged in age from 12 to 45 years