Ignition is usually the easiest of the three to check because on most engines, all you have to do is pull off a plug wire and check for spark when the engine is cranked. On coil-over-plug DIS systems, there are no plug wires so you have to remove a coil and use a plug wire or adapter to check for a spark.
Stress can affect every part of your body. muscle aches, head aches, how your hair grows, the texture of your skin, it can affect your menstrual cycle.
The key brain regions involved in the stress response may be altered at the chemical or cellular level. Changes might include fluctuations in the concentration of neurotransmitters or damage to nerve cells.