This is probably kinda a stupid question but do any of you know if pulling your hair could affect the speed of wich it grows? I've heard biting your fingernails could have that effect since you're sort of pulling them at the same time. Or could it possible damage the hair pulling it?
That's a myth. You'll just end up damaging your hair. A friend of mine swears by it; she also thinks that by brushing her hair all the time it makes it grow faster. Not at all true.
Brazjol's right, 'tis just a myth. My aunt, who owns a hair salon of all things, swears by it herself. She kept telling me to slick back my hair 24/7 and always have it ponytailed so the roots would be "pulled out" and would grow longer faster. Dangerous advice.
Long hair tends to grow faster than short hair because there is more weight on it than there is on short hair, but anything past the weight of the strand itself is either unimportant or dangerous.
Constantly pulling your hair TIGHT, like really really honking major tight "I have a facelift" tight, will result in traction alopecia (hairloss) from the root being pulled on too much too often.