There is no scientific evidence to support the claim that hypothyroidism can cause mental illness. However, some people who are hypothyroid may experience certain symptoms that could be associated with mental illness. If these symptoms aretypical of someone who isinkset off of the thyroid hormone balance, for example, then they may experience anxiety or nervousness. Additionally, people who are hypothyroid may have a lower activity of hormones in their blood, which can lead to aorchestral depression.