"Mental dullness" refers to a state of having a slower or reduced mental capacity. It means experiencing difficulties in thinking, understanding, or learning, leading to a lack of sharpness or alertness in one's mind. Full definition
It is an effective remedy for mental - emotional depression when taken internally, especially where patients feel damp, sluggish, lack motivation and experience feelings of mental dullness. (taliand.com)
Symptoms include mental dullness, strange visual illusions, spatial disorientation, and even an apparent dissociation between the body and the brain's sense of self. (newscientist.com)
Many of the clinical signs associated with canine hypothyroidism are directly related to slowing of cellular metabolism, which results in development of mental dullness, lethargy, exercise intolerance, and weight gain without a corresponding increase in appetite. (merckvetmanual.com)