Familial load as a continuous variable

Additionally, FL was analyzed as a continuous variable, measuring the total load of psychiatric disorders among first-degree relatives. We used the Family Liability Index (FLI), which has also been used to analyze FL in high-risk individuals [24]:

The Family Liability Index (FLI) reflects the aggregation of psychiatric disorders among a participant’s first-degree relatives. The FLI is estimated based on the presence of psychiatric disorders in the biological mother (BM), the biological father (BF), biological siblings (BS) and biological half-siblings (HS). The index considers that half-siblings share only half the genetic information compared to parents and full siblings. The estimate indicates the load of diseased first-degree relatives in the numerator compared to the number of first-degree relatives (the family size) in the denominator. The FLI continuously assumes values from 0 to 1, with 0 reflecting “low familial load” and 1 reflecting “high familial load”.