Lithium has been prescribed for those with manic depression for decades. It is given to patients with mood disorders that tend to be disabling or recurring. People who have a high risk of suicide are given lithium because it has been proven to reduce the rate of suicide with depression. The purpose of the medication is to prevent a relapse of serious depression symptoms. It use to be given just to those with bipolar disease, but it is now being given to those who have any kind of mental unstableness because it will calm the mood swings and help a person feel normal once again.
When it comes to bipolar depression, a person has strong suicidal tendencies and the premature death is caused by stress-related illness or from substance abuse. In many studies of lithium, it has been shown that it can decrease the chance of someone committing suicide and it also helps take a little bit of the edge off. Lithium was not made to make a person stop thinking about death, but it was made to stabilize the mood swings. Once the mood swings are stable and a person feels a bit more "normal" usually, the thoughts of suicide or death will go away. It also has been proven to help decrease the side effects of serious depressions and bipolar behavior once taken for a couple years.
Like all drugs, lithium has its effects. It does decrease the rate of suicides or even attempts, but it has been proven that once patients are off the medication, their condition will worsen. Many people will commit suicide after being on lithium for long periods of time and then taken off the medication. Within a year, most patients will at least attempt to end their life.
However, even though, lithium can control a person's suicidal tendencies, it cannot control the disorder that causes them. It doesn't help a person's mental health other than the fact that it doesn't allow a person to have suicidal thoughts because of their depression. Depression is not cured by lithium, but the side effects will become less severe.