Valeri Polyakov spent 437 days on the space station "Mir" - an environment at least an order of magnitude more limited than Mars, I'd say. Wikipedia has this in

Valeri Polyakov spent 437 days on the space station "Mir" - an environment at least an order of magnitude more limited than Mars, I'd say. Wikipedia has this information about his mission: "Polyakov underwent medical assessments before, during, and after the flight. He also underwent two follow-up examinations six months after returning to Earth. When researchers compared the results of these medical exams, it was revealed that although there were no impairments of cognitive functions, Polyakov experienced a clear decline in mood as well as a feeling of increased workload during the first few weeks of spaceflight and return to Earth.[6][7] However, Polyakov's mood stabilized to pre-flight levels between the second and fourteenth month of his mission. It was also revealed that Polyakov did not suffer from any prolonged performance impairments after returning to Earth. In light of these findings, researchers concluded that a stable mood and overall function could be maintained during extended duration spaceflights, such as manned missions to Mars."