低。
He often alternates from one extreme to another. 他常走极端。
4.step up：逐步增加
5.fell by a third：下降了三分之一
介词by可以用来表示升高、增加或降低、减少的程度。
6.something modern psychologists would certainly recognize：而这些病情现代心理学家一定能够识别出来。
something是前面“heavy moods of deep depression”and many times of“intense nervous irritability”的同位语,something后面是个定语从句,省去关系代词that。
练习：
A The number included five who had not found any relief using drug treatment.
B Long and brisk walks are not necessarily beneficial to every person.
C They studied 12 people with severe depression that had lasted an average of nine months.
D The outcome indicated a clinical benefit which could not be obtained with pharmacological treatment currently available, they said.
E This is also the advice that experts from the Free University in Berlin are giving today.
F According to the regime, intense activity lasting three minutes was alternated with walking at half speed for three minutes.
答案：1.E 2.C 3.F 4.A 5.D
