How can i tell if my brother is addicted to drugs?

Changes sudden: Loss of appetite, increase in appetite, any changes in eating habits, unexplained weight loss or gain. Slowed or staggering walk; poor physical coordination. Inability to sleep, awake at unusual times, unusual laziness. Red, watery eyes; pupils larger or smaller than usual; blank stare. Cold, sweaty palms; shaking hands. Puffy face, blushing or paleness. Smell of substance on breath, body or cloth.