Is it permissible to commit suicide by non-painful methods, such as using helium gas, due to a chronic mental illness (autism) that causes a complete inability to engage in social and professional interaction, and leads to a life akin to death?

It is never permissible to commit suicide, for a person does not own their soul to dispose of it. Killing oneself exposes its perpetrator to Allah’s punishment and wrath. Suicide does not solve problems; rather, it transfers a person to something more severe. Patience and recourse to Allah through supplication are better for a person.