Biological in uence: includes causal factors from the eld of genetics and neuroscience. Psychological in uences: include causal factors from behavioural and cognitive processes. Developmental in uences one dimensional or multidimensional models. One dimensional : this means you just look at one single cause. Most clinicans believe there is a multidimensional. Conditioned response to sight of blood, even words produce the reaction. Tendency to escape and avoid situations involving blood. Vasovagal syncope: heart rate and blood pressure increase, body overcompensation (common cause of fainting) Jodis fainting causes disruptions at home and school: friends rush to help him, got suspended, doctors say nothing physically wrong. Certain times of our lives we enter a developmental critical period when we are more or less reactive to a given situation or in uence than at other times. Jodi bene ted from the brief but intensive treatment at clinic and was back to school within 7 days.