Answer:
True
Step-by-step explanation:
One way trip to mars will take anywhere between 150-300 days depending on the alignment of Mars-Earth and the speed of launch. The round trip will easily be of around 2 years. For this whole journey the astronaut will be in micro-gravity environment and out of the safety of Earth's atmosphere. The gravity is very critical for a healthy person and long exposure to micro-gravity environment will have its adverse effects on astronauts.
Astronauts will also be exposed to a lot of radiation which is blocked by atmosphere on Earth. This exposure is very dangerous and long exposure to such radiation might be cancerous as well.
Not to forget the adverse psychological impact on Astronauts from the long journey.