Loosely and largely nontechnically, descriptive of
persons of elevated emotionality, hyperexcitability, tenseness. By extension,
referring to a broad class of disorders whose origins may be either neural or
emotional. The looseness of usage has led to a gradual abandonment of this term
in the technical literature, although it survives in popular parlance, e.g.,
nervous breakdown for a serious acute emotional disorder and nervous energy for
an elevated level of drive and activity.