Anxiety symptoms were measured using items from the PHQ, a short screening measure for assessing anxiety severity [33]. There are seven items in the PHQ based on the DSM-IV criteria. All participants are asked an initial question (“how often have you been bothered by feeling nervous, anxious, on edge, or worrying a lot about different things in the past four weeks”), and those who answer on “several days” or “more than half the days” are subsequently asked six anxiety-related questions with the answers "yes” (score = 1) and "no" (score = 0). Once a total scale score was generated, a validated cut-off point (score > = 3) was used to indicate a clinical level of anxiety (representing a likely anxiety disorder) (coded 1) vs lower anxiety (coded 0) [34].
During the face-to-face interview, interviewers implemented the Composite International Diagnostic Interview (CIDI), with participant responses used to generate a diagnosis of 12-month Generalised Anxiety Disorder (GAD). The CIDI items were coded according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM–5-TR) criteria [26]. More specific than the broader GADS and PHQ screening scales, the DSM-5-TR classifies GAD when people have experienced excessive anxiety and worry with more than two symptoms for at least six months.
Covariates
A range of sociodemographic variables known to be associated with WFC and anxiety were considered. These variables included gender, number of negative life events, education, income, presence of children (< 5 years), work hours, relationship status, housework distribution, physical health problems, smoking and alcohol use, personality, and anxiety symptoms in a previous wave of data collection (Wave 3) [32], [35].
The number of negative life events were summed and divided into three categories: none (coded 0), one (coded 1), and two or more events (coded 2+). Participants were asked about negative life events during the past 6 months using an extended version of the List of Threatening Experiences Questionnaire [36] and questions from the British National Survey of Health and Development [37]. Analyses included 16 items about adverse events in the past six months, including serious illness, injury, assault of a close relative or yourself, death of a close family member or friend, relationship separation, serious problems within close relationships, financial crisis, work disappointments, legal problems, marital difficulties, and loss of something valuable.
Housework distribution was assessed by asking whether the participant was 100%, 75%, 50%, 25% or 0% responsible for housework. These responses were coded into three categories: 100% responsibility (indicating higher role strain in domestic duties) (coded 1), 50%-75% responsibility (coded 2), and less than 50% responsibility (coded 3).
Work hours were recoded to represent short part-time hours (less than 30 hours) (coded 1), medium part-time to full-time hours (30–49 hours) (coded 2) and long-full time hours (over 50 hours or equivalent) (coded 3).
Income levels were coded into three categories: low-income group (less than $1075 per week) (coded 1), median-income group ($1075-$3800/week) (coded 2), and high-income group (more than $3800 per week) (coded 3).
Smoking status and alcohol behaviour was asked about using the following items: “do you currently smoke?” and “how do you classify your drinking behaviour?” with the possible responses to the alcohol item “abstain” (0), “occasional” (1), “light” (2), “medium” (3), “hazardous” (4), and harmful (5). The response to the smoking item were grouped into “current smokers” (coded 1) and “not current smokers” (coded 0). The responses to the alcohol item were grouped into “abstaining or moderate drinkers” (scores 0 to 3 coded as 0) and “hazard drinkers” (scores 4 to 5 coded as 1).
Physical health problems were derived from self-reported checklist of chronic physical health disorders included epilepsy, asthma, chronic bronchitis, emphysema, diabetes, thyroid, heart problems, arthritis, and Parkinson’s Disease. This variable was coded into binary categories with respondents with no medical conditions labelled as “no conditions” (coded 0), and those with any medical condition coded as “at least 1 condition” (coded 1).
Psychosocial job characteristics were evaluated in four areas: job demands, job decision/control discretion, job skill discretion and job security [38]. There were four items assessing job demands such as “Do you have to work very fast?” Job decision or job decision/control was assessed by nine items such as “Do you have a choice in deciding how you do your job?”. Job skill represented job skill discretion using six items such as “Does your job provide you with a variety of interesting things?” All the above questions included four response options: “often”(4), “sometimes”(3), “rarely”(2) and “never”(1), and responses were summed within each psychosocial job domain to form a scale where higher scores represented lower job quality. A tertile cut-off point was then used to determine “high” (coded 1) and “low” (coded 0) job demands, job control and job skill. Job security was evaluated by a single item – “How secure do you feel about your job or career future in your current workplace?” with four response categories scored from 1 to 4 (“not at all secure”, “moderately secure”, “secure”, “extremely secure”). Respondents with score 3 and 4 were classified as having high (coded 1) job security, with responses 1 and 2 classified as low (coded 0) job security [39].
Personality (emotional stability) was measured by the Ten-Item Personality Inventory (TIPI) [40]. There were 10 items from the TIPI included in the questionnaire, with two specifically assessing emotional stability. The items are “I see myself as” (a) “anxious and easily upset”; (b) “calm and emotionally stable”. These two questions were responded to on a 7-point scale ranging from 1 “Disagree strongly” to 7 “Agree strongly”. These items were summed to provide a total score ranging from 2 to 14 where a higher score represented less emotional stability.
Anxiety symptoms in Wave 3 were measured by seven items in the PHQ in Wave 3 using the same cut-points as previously described (i.e. the same items used in Wave 5).