too easily upset or offended

impressionable

easily influenced

easily taught; gullible

physically or mentally weak (especially through age)

sick, weak

of the soul or mind; of phenomena and conditions which appear to be outside physical or natural laws, e.g. telepathy

extrasensory in perception

reacting easily or quickly

quick to react

quickly or easily receiving impressions; (of feelings) easily hurt or offended; (of instruments) able to record or reproduce small changes

impressionable

easily influenced by feelings

exposed, naive