Lithium

Hair lithium measures the amount of lithium present in a sample of scalp hair. Researchers have studied it as a possible marker of environmental exposure, but it hasn't been validated for diagnosing a nutritional deficiency, predicting mental illness, or guiding treatment.

This is a research-stage measurement. Differences between groups sometimes track differences in exposure, but an individual result can't reliably establish how much lithium you consume or how much is present in your brain. There is no established hair concentration to aim for to improve mood, memory, or longevity.

What Hair Records

Lithium can enter growing hair from the circulation. Material can also reach the strand through sweat, water, dust, and hair products. The measured amount can therefore include both material incorporated during growth and material deposited afterward.

Hair near the scalp grew more recently than hair farther along the strand. Its length provides an approximate historical window, but growth rates, external exposure, and sample preparation complicate the timing. A hair result is not a calibrated average of your blood lithium or dietary intake over a fixed number of months.

The laboratory measures total elemental lithium using ICP-MS. This technique identifies elements by their atomic masses. Results are reported in µg/g, or micrograms of lithium per gram of hair. The measurement doesn't identify whether the lithium came from food, water, a supplement, medication, or external contact.

Mood, Behavior, and Suicide

Some older hair studies reported lower lithium concentrations in selected groups, including people convicted of violent crimes. These comparisons couldn't establish that low lithium caused the behavior. A study of 200 Tokyo residents proposed a connection with suicide risk, but it didn't follow participants to see whether hair lithium predicted suicide.

A later autopsy study directly compared hair from 25 people who died by suicide with hair from 27 people who died of other causes. It found no statistically clear difference in lithium concentrations. The small sample leaves uncertainty, but it provides no basis for using a hair result to assess your personal suicide risk.

Research on lithium in drinking water asks a related question using a different measurement. A meta-analysis of studies covering 939 regions and a large population cohort found an inverse association between water lithium and suicide mortality. Its pooled estimate used unadjusted associations, mostly comparisons between places. Regional differences in income, health care, and other exposures could influence the findings. They don't establish a protective hair concentration.

Glioma Research

A case-control study in southeastern China measured 35 elements in the hair of 100 people with glioma and 128 comparison participants. Gliomas are tumors arising from cells related to the brain's supporting cells. Higher hair lithium was associated with greater odds of glioma after adjustment for several personal and environmental factors.

Hair was collected before treatment but after diagnosis, so the study couldn't establish whether the exposure preceded the tumor. Other exposures, changes associated with illness, and chance could contribute to the result. This finding doesn't establish that lithium causes glioma or that hair testing can screen for it.

Children and Neurodevelopment

Hair studies in children with autism have produced inconsistent findings. One study reported lower hair lithium particularly among younger children with autism and their mothers. Another study, which also combined its findings with earlier research, found no association between hair lithium and autism. These results don't establish a lithium deficiency or support using hair lithium to diagnose or explain autism.

When Results Can Be Misleading

Several limitations come from research on hair element analysis generally. Their exact size and direction haven't been established specifically for lithium in every setting.

• Chemical treatments: dyes, bleach, and straightening products can alter hair composition. You can't assume that every treatment lowers lithium by a predictable amount.
• External contamination: water, dust, sweat, and products can contribute material to hair. Laboratory washing doesn't reliably separate everything deposited externally from everything incorporated during growth.
• Sample selection: collection site, strand length, and the amount of treated versus untreated hair can change what periods and exposures the sample represents.
• Laboratory methods: washing, digestion, calibration, and measurement sensitivity can affect results. Differences between laboratories can be mistaken for changes in exposure.

Interpreting Changes Over Time

A change between samples may reflect a change in exposure, but collection and laboratory differences are alternative explanations. There is no validated amount of change that proves your health has improved or worsened. Using consistent collection and analysis reduces some uncertainty without turning a personal baseline into a clinical target.