A mood stabilizer is a psychiatric medication designed to even out the extreme emotional highs and lows of bipolar disorder. These drugs reduce symptoms of mania (racing thoughts, risky behavior, sleeplessness) and help prevent depressive episodes from returning. While bipolar disorder is the primary reason they’re prescribed, the term “mood stabilizer” isn’t a single drug class. It’s an umbrella that covers several different types of medication, each working through slightly different pathways in the brain.
How Mood Stabilizers Work
The biology behind mood stabilizers isn’t fully mapped, but the leading theory points to problems with how brain cells adapt and communicate. In bipolar disorder, the brain’s electrical signaling and chemical messaging systems swing too far in both directions. During mania, neural circuits become overexcited. During depression, they become underactive.
Mood stabilizers appear to dampen these swings by influencing how brain cells fire and how chemical signals pass between them. Early research focused on shifts in charged particles (ions) moving across cell membranes, which directly affect how excitable a neuron becomes. More recent work has identified effects on multiple signaling systems inside cells, essentially recalibrating the brain’s ability to respond to stimulation without overshooting in either direction. The result, when the medication works well, is a narrower emotional range that stays within functional bounds.
The Main Types of Mood Stabilizers
Lithium
Lithium remains the oldest and most studied mood stabilizer. It’s a naturally occurring element (not a synthetic drug) and has been used in psychiatry since the mid-20th century. International treatment guidelines consistently rank it as a first-line option for acute mania, bipolar depression, and long-term maintenance. It’s particularly effective at preventing manic episodes, though it also reduces the risk of depressive relapses.
The challenge with lithium is its narrow safety window. The difference between a therapeutic dose and a toxic one is small, which means regular blood tests are necessary. Too much lithium can cause nausea, vomiting, diarrhea, tremors, slurred speech, and in severe cases, seizures or kidney damage. Even at safe levels, long-term use requires monitoring of kidney function and thyroid levels, typically every six months.
Anticonvulsants
Several medications originally developed for epilepsy turned out to be effective mood stabilizers. The most commonly used are valproate (divalproex), lamotrigine, and carbamazepine. Each has a different strength profile.
Valproate is a first-line treatment for acute mania and long-term maintenance. It tends to work well for people with rapid mood cycling or atypical presentations of bipolar disorder. Like lithium, it requires blood monitoring, particularly liver function tests during the first six months. Carbamazepine occupies a similar niche. In comparative studies, lithium outperformed carbamazepine for “classic” bipolar disorder, while carbamazepine showed stronger results for atypical forms, such as those with additional psychiatric conditions or unusual psychotic features.
Lamotrigine stands apart because its primary strength is preventing depressive episodes rather than manic ones. In a head-to-head comparison lasting a year and a half, lithium was significantly better at preventing mania, while lamotrigine was superior at keeping depression at bay. This makes lamotrigine especially useful for people whose bipolar disorder leans heavily toward the depressive side. One important caveat: lamotrigine must be started at a very low dose and increased slowly over weeks. Raising the dose too quickly increases the risk of a serious skin reaction. Fast dose increases carry roughly eight times the risk of developing a rash compared to standard schedules, and that rash can, in rare cases, become life-threatening.
Atypical Antipsychotics
A newer category of mood-stabilizing treatment comes from atypical antipsychotics. These were originally designed for schizophrenia but have proven effective for bipolar disorder as well. Quetiapine is the most versatile of the group. It’s approved for acute mania, bipolar depression, and maintenance therapy, and it’s a first-line recommendation across nearly every phase of bipolar disorder in current guidelines.
Five atypical antipsychotics are FDA-approved specifically for bipolar depression: cariprazine, lumateperone, lurasidone, the combination of olanzapine with fluoxetine, and quetiapine. Of these, only cariprazine and quetiapine also treat manic episodes. Others, like aripiprazole and risperidone, are first-line options for mania and maintenance but aren’t approved for the depressive phase.
How Doctors Choose Between Them
Treatment guidelines from the Canadian Network for Mood and Anxiety Treatments and the International Society for Bipolar Disorders rank options hierarchically, meaning medications listed higher are generally tried first. For acute mania, lithium, quetiapine, and valproate sit at the top. For bipolar depression, quetiapine and lithium lead the list alongside lamotrigine and newer options like cariprazine and lurasidone. For long-term maintenance, lithium, quetiapine, valproate, and lamotrigine are all first-line choices.
In practice, the choice depends on the individual’s symptom pattern. Someone with frequent manic episodes might start with lithium or valproate. Someone whose main burden is depression might benefit more from lamotrigine or quetiapine. Combination therapy is common too: pairing lithium or valproate with an atypical antipsychotic often works better than either alone for severe episodes. Age matters as well. For children and adolescents, lithium, risperidone, and aripiprazole are first-line for mania, while lurasidone leads for depression. For older adults, lithium and valproate remain the go-to options for mania, with quetiapine preferred for depression.
What Taking a Mood Stabilizer Looks Like
Starting a mood stabilizer is rarely immediate. Most require a gradual dose increase over days or weeks to minimize side effects and find the right level. Lithium requires blood draws within the first week or two to check levels, then periodically during the first six months, then at least every six months long-term. Kidney function and thyroid hormone levels are checked on a similar schedule because lithium can affect both organs over time.
Valproate requires liver function monitoring during the first six months especially. Carbamazepine needs both liver and kidney monitoring every six months. Lamotrigine is less demanding on bloodwork but requires patience during the slow titration period, which typically takes four to six weeks before reaching a full dose.
Side effects vary by medication but commonly include weight gain (especially with valproate and some antipsychotics), drowsiness, tremor, digestive upset, and increased thirst or urination with lithium. These effects are often manageable, and many ease with time or dose adjustment.
How Long Treatment Lasts
The World Health Organization recommends that maintenance therapy with mood stabilizers continue for at least six months after symptoms go into remission, balancing effectiveness against side effects and the individual’s preferences. In reality, most clinicians recommend significantly longer courses. Bipolar disorder is a lifelong condition, and stopping medication is one of the most common triggers for relapse. Many people stay on mood stabilizers for years or indefinitely, particularly after multiple episodes.
Stopping should never be abrupt. Tapering off gradually, under medical supervision, reduces the risk of a rebound episode. The decision to continue or discontinue is highly individual, shaped by how many episodes someone has had, how severe they were, and how well they tolerate the medication.
Mood Stabilizers and Pregnancy
Pregnancy planning requires careful thought for anyone on a mood stabilizer. Lithium carries a small but real risk of a specific heart defect called Ebstein’s anomaly in the baby. The baseline rate of this defect is about 1 in 20,000 births; with lithium exposure during the first trimester, that rises to roughly 1 in 1,000. The overall rate of major malformations with lithium is also somewhat higher than the general population (about 7.4% compared to 4.3%). Valproate carries its own well-documented risks and is generally avoided during pregnancy whenever possible.
Lamotrigine is often considered the safest option for people who need mood stabilization during pregnancy, though the decision always involves weighing the risks of medication against the risks of untreated bipolar episodes, which themselves pose dangers to both parent and baby.