Let's first clear up a few confusing statements in your question:
1. Nobody can become crazy because of too much studying. Rather, one can become mentally tired or exhausted because of too much studying; but not crazy. Possible reason(s) for “becoming crazy or mad” are either organic in nature (brain damage) or unknown (idiopathic). Madness due to brain damage is called psycho-organic syndrome. Madness due to idiopathic reasons is called psychosis. Psychoses are probably genetically conditioned. Psychoses include schizophrenia, bipolar disorder, paranoia, paranoid conditions, etc.
2. A shot or injection that will prevent someone from becoming crazy does not exist! There are medications that exist for treating, but not for preventing, madness. For example, anti-psychotics, antidepressants, and anxiolitics are medicines used for treating “madness” and “craziness”.
Cerebral atrophy is not a specific brain disease but only a pathologic term for organic damage of the brain. During this condition, the brain (especially the cortex) decreases its dimensions (atrophy). Brain atrophy causes disorders in all 3 main brain functions: sensory perception (senses), motor movement, and cognitive perception(emotions, memory, thinking, intelligence). Cerebral atrophy can be seen on a CT-scan.
You should consult a neurologist and psychiatrist if you'd like a clear diagnosis and more information on treatment options, when necessary.