A plethora of empirical data support a positive (or “brighter”) pathway to optimal human functioning as specified within Basic Psychological Needs Theory (Ryan and Deci in Psychol Inq 11(4):319–33, 2000). Yet, far less is known about the negative (or “darker”) pathway, a process evoking of human dysfunction and ill-being (cf. Vansteenkiste and Ryan in J Psychother Integr 23(3):263, 2013). Further, debate surrounds the independence and interplay between psychological need satisfaction and psychological need frustration and how these dynamic constructs are experienced within individuals. In this work, variable and person-oriented analyses were employed to: (i) investigate the relationships between the basic psychological needs and symptoms of stress, depression and anxiety as well as with life satisfaction; and (ii) identify different psychological need profiles and their relationship with psychological function. Participants (N = 2236; M Age = 42.16 years; SD = 7.8) were UK-based operational firefighters who completed an online survey. Results of regression analyses showed a moderating effect of psychological need satisfaction on the relationship between need frustration and negative psychological symptoms. Latent profile analyses revealed five distinct basic psychological need profiles that carry implications for human psychological functioning. Some support for an asymmetrical relationship between need satisfaction and need frustration emerged (Vansteenkiste and Ryan in J Psychother Integr 23(3):263, 2013), yet, examples of above average need satisfaction and frustration scores were also observed. Worker profiles where psychological need frustration prevailed over need satisfaction had the poorest psychological health.