Yes too much sleep can cause health and mental effects. The right amount of sleep should range between 6 to 8 hours. Any sleep that's over 10 hours is regarded as an oversleep. Oversleep is brought by diet or health complications. Oversleeping has effects on your diet and some of them include, stroke, diabetes, heart diseases, depression among other health effects.The most dangerous part affected is the brain. Oversleeping may affects your moods and your mental health in general. Increased in sleep duration may lead to depression or anxiety symptoms. Actually, this isn't only brought by oversleeping but also getting little sleep. Its good to take precautions to avoid oversleeping and some of the include. You should always take a 20/ 30 minutes nap everyday and should not in the late evening, eat a well balanced diet and finally take plenty of water. Water and rest go hand in hand.