Mood stabilizers are medications used primarily to treat bipolar disorder, a condition in which a patient experiences extreme mood swings. Mood stabilizers are effective in reducing these swings when symptoms are occurring and in preventing new episodes.

It appears bipolar disorder occurs when there are too many or too few neurotransmitters, which convey messages between nerve endings in the brain. Mood stabilizers work by changing these neurotransmitter levels and by affecting how they interact with the nerves within the brain.

The most commonly prescribed mood stabilizers are lithium and the anticonvulsants valproate, carbamazepine and lamotrigine. Many other anticonvulsants (e.g., topiramate) are also considered to be mood stabilizers. Many atypical antipsychotics (e.g., olanzapine, risperidone) also have mood stabilizing effects and are thus commonly prescribed even when psychotic symptoms are absent. Though mood stabilizers treat bipolar disorder in particular, they may also be used to treat some personality disorders (e.g., borderline personality disorder [BPD]).

Mood stabilizers require careful monitoring because they can cause many side effects, including nausea, tremors and weight gain. In the case of lithium, the therapeutic dose is very close to the toxic dose, which increases the risk of toxicity.

Symptoms of mood stabilizer toxicity include nausea and vomiting, tremors, seizures, confusion and fainting. Overdose can result in coma and may be fatal. Mood stabilizers may not be safe for patients with conditions affecting the kidneys, liver, heart or blood. In addition, mood stabilizers can interact with many other medications.

Many mood stabilizers are associated with birth defects or developmental problems if taken during pregnancy. Certain mood stabilizers may not be safe for breastfeeding mothers. Therefore, women who are pregnant or may become pregnant and women who intend to breastfeed should consult an obstetrician before taking mood stabilizers.

Lithium is the most commonly prescribed mood stabilizer for children and adolescents, though carbamazepine or valproate may also be used. However, valproate is generally not recommended in pubescent girls younger than age 20. Valproate can increase testosterone levels in teenage girls, which may lead to the development of polycystic ovarian syndrome (hormonal disorder characterized by abnormal hair growth and fertility problems). Although dosages for elderly patients may be lower, treatment and response to mood stabilizers is essentially the same in older adults as in younger adults.