 This study investigates the neuroprotective properties of low-dose lithium in young individuals at ultra-high risk of developping a first psychotic episode. Fourty individuals having some symptoms of an emerging psychotic disorders without meeting the threshold for a full-blown mental illness will be treated with a low dose of lithium about a third of the dose that is usually used to treat acute mania. We will assess the progression of the conditions of these individuals on a montly bases for a year. We will do behavioural, cognitive and imaging assessments prior start of the treatment, after three months and one year. We hope to demonstrate that low dose lithium will stop or even reverse the progression of disease. We expect that behavioral, cognitive and in vivo brain imaging parameters in those individuals treated with low dose lithium improve, compared to the monitoring group. 