King's College London

The main goals are to see if the supplement increases lithium levels in their blood, how much people take it, and any positive or negative experiences.

People will be asked to take the supplement daily and come for five visits to the research site at the King's College London Denmark Hill campus in south London, over a six-month period time. We will work with you to arrange days that are convenient for you.

Each appointment includes:

• Blood test: this is very quick and similar to most blood tests you would have in usual care.
• Thinking skills exercises: These are exercises measuring things like memory, concentration, planning and reasoning. They take about 15 minutes.
• Questionnaires: With the researcher, questionnaires are about things like illness experiences, daily life functioning, quality of life, mood and sleep quality.

Lithium is known to improve mood and daily life for people with bipolar disorder and depression, and may also help those with dementia, suicidal thoughts, or certain viruses. While we are using lower doses in this study, we hope that people might experience benefits in mood, thinking, or other areas. Either way, participants will help us understand if supplementary lithium can benefit people with mood and brain-related conditions.

For each of the five visits, people will receive £24 as a token of appreciation and participation in the study, and some travel expenses.

We are looking for participants with a type of depression called ‘mixed features’.

To be eligible, you need to:

• Be aged between 18-65 at study entry.
• Be experiencing depression of this mixed features type.
• Be taking medication for depression, stably, for at least six weeks.
• Be willing to try a commercially available lithium supplement.
• Be willing to attend planned study visits.