Yes, thyroid disease can affect your mood primarily causing anxiety and depression. The more severe the disease the more severe the mood swings. If you have hyperthyroidism, overactive thyroid, you may experience unusual nervousness, restlessness, anxiety, and irritability. On the other side of the spectrum, if you have hypothyroidism, underactive thyroid, you may experience mild to severe fatigue and depression. Monitor your thyroid levels regularly and manage them well with medications as prescribed and make necessary lifestyle changes.