Study Overview: This study tests if a single shot of RE104 can help with bad moods or anxiety in people who have a medical illness like cancer, ALS (a disease affecting nerves), MS (a disease affecting the brain and spine), PD (a condition that impacts movement), or IPF (a lung disease). Eligibility: To join, you must have felt sad or anxious for at least 4 weeks because of a medical issue. You should be able to walk and take care of yourself, have normal thinking skills, and either not be using antidepressants or be stable on them. If you're female, you shouldn't be pregnant or planning to be, and males shouldn't plan to make a partner pregnant. You should agree to follow all study rules. People at risk of suicide, with certain mental disorders, or with certain other health issues cannot join. Key Points:

• The study involves taking one dose of RE104.
• You must be able to attend all study visits and follow study rules.
• Some medical conditions or medications might prevent participation.