So back at it....
"Studying Spells from Madness"
Long-term study of the arcane arts leaves an indelible mark on the mind of its practitioners, as spells are memorized, then ripped from the mind as the spell is spent... It goes without saying that a wizard's mental health will be affected by this, as would any long-term user of a dangerous and unstable substance.
Some become twisted and fevered, and some use their mental scarring to twist the spells through their own machinations...
5% chance per level of developing mental illness. Randomly determine disorder.
1. Mania - +10% effect or duration to speed-related spells (Haste/Slow); -10% effect or duration to physical manipulative spells (floating disk, levitate, repulsion, telekinesis)
2. Paranoia - Doubles duration of physical defensive spells (Shield, protection from missiles, Wizard lock); Unable to use Charm or Suggestion spells.
3. Anxiety - 2x duration or radius for "protection from" spells, magical or incorporeal (Dispel magic, protection from evil); Requires extra round to cast other spells due to OCD (ex. sorting components, extra ritual).
4. Bipolar - During manic episode - doubles duration or effect of charm, suggestion, growth spells; during depressive episodes - halves for same.
5. Psychosis - +10% effect or duration to illusions/perception (Phantasmal force, invisibility); +10% chance of failure for "comprehension" spells (Read language, ESP, Clairaudience/Clairvoyance)
6. Impulse control/substance addiction - Functional addiction - normal performance may only occur under the influence of selected drug/substance - if 'cold turkey' - 25% diminished range/duration + 10% chance of outright spell failure.
This is a very quick conceptual exercise under the usual self-imposed deadline and a first cut based on how I think that various disorders may affect different spell 'families.' Many writers have come up with side effects for use of both individual spell and long-term magic use - I suspect that I will revisit this sometime down the road, as well. As always, feel free to use and abuse.