If you're suffering from major depression, would amphetamines work. if not, what would it do instead of working?

Not by themselves: Ritalin (methylphenidate) has sometimes been given to augment antidepressants in treatment-resistant depression, but amphetamines do not reliably treat depression by themselves. Used alone, any lightening of mood would have a daily wear-off effect. Also there could be increased tension, irritability, and jitteriness -- not pleasant for someone who already has an agitated-type depression.