There are many reasons for finger nail depression, such as trauma, fungal infection, psoriasis and so on. 1. Trauma: Fingernail trauma can cause the phenomenon of fingernail depression. 2. Fungal infection: Finger nails are infected by fungus, which can lead to changes in nail color and shape, such as grey and yellow thickening, depression, debris, etc., which can gradually spread to other nails. 3. Psoriasis: when psoriasis involves the fingernails, it can lead to the depression of the fingernails, and it may also be accompanied by horizontal grooves on the nails, turbidity and other phenomena. There are many reasons for finger nail depression, it is recommended to go to the hospital in time to improve the examination and take standardized treatment according to the doctor’s instruction after clear diagnosis.