Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:…stress in schizophrenia (Figure 1), the results reported here may indicate that the DA-dependent restitutive system, which normally decreases its own activity in the face of stress, may be disrupted or already down-regulated in schizophrenia, as previously predicted (Friedhoff 1985, 1986, 1988).
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